BBC Sky at Night

RISING RUBIN

This was Sylvia’s promise to you...

A generation ago, a woman named Sylvia made a promise. As a doctor’s secretary, she’d watched stroke destroy the lives of so many people. She was determined to make sure we could all live in a world where we’re far less likely to lose our lives to stroke.

She kept her promise, and a gift to the Stroke Association was included in her Will. Sylvia’s gift helped fund the work that made sure many more of us survive stroke now than did in her lifetime.

Sylvia changed the story for us all. Now it’s our turn to change the story for those who’ll come after us.

Stroke still shatters lives and tears families apart. And surviving a stroke is just the start of a long and gruelling recovery journey. If you or someone you love has been affected by stroke – you’ll know just what that means.

You can change the story, just like Sylvia did, with a gift in your Will. All it takes is a promise.

You can promise future generations a world where researchers discover new treatments and surgeries, and stroke survivors and their families have the support to find the strength and determination they need to find their way back to life.

Finding strength through support

Your promise today gives strength for tomorrow. Please, leave a gift in your Will to the Stroke Association.

Find out how by calling 020 7566 1505 or email legacy@stroke.org.uk or visit stroke.org.uk/legacy

20 years in the making: it’s time for the Rubin revolution!

Dramatic as it was to see the first images from the Vera Rubin Observatory in June, it’s nothing compared to what we can expect when its groundbreaking sky survey begins in earnest later this year. This will be the largest astronomical survey ever, generating around 20 terabytes of data nightly as it captures the entire southern sky every few nights. It helps to have the world’s largest digital camera on board – a three-tonne giant whose 189 sensors combine to give a resolution 66 times greater than that of the latest smartphone. Science writer KR Callaway travelled to Chile to tour the observatory and meet the team bringing this ambitious project online. Read her fascinating feature on page 28

Rubin’s survey will be open-access, meaning it will be freely available to scientists from every branch of astronomy. But for amateur astronomers, its estimated final size of 500 petabytes may be a bit much to handle! Thankfully, there are many resources out there that organise the cosmos into more manageable chunks. Join Pete Lawrence on page 68 as he delves into the essential star catalogues every astronomer should know.

As one exciting new project begins, another comes to an end. This month sees the scheduled conclusion of NASA’s groundbreaking Juno mission to Jupiter. On page 34, Nicky Jenner uncovers how its nine years in orbit around the gas giant have produced a trove of discoveries far beyond what we’ve learned from any previous mission.

Enjoy the issue!

Chris Bramley, Editor

PS Our next issue goes on sale on Tuesday 16 September.

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To get started, check out our guides and glossary at www.skyatnightmagazine.com/astronomy-for-beginners

This month’s contributors

KR Callaway Science journalist

“I’ve never seen as many stars as I did in the Chilean Andes, visiting the Vera Rubin Observatory. I can’t wait to see what it will unveil with its far keener eye!” Read how Rubin will change everything, page 28

Nicky Jenner Science writer

Jamie Carter

Astronomy journalist

“Next year will see the first of a celestial hat-trick for Spain: three solar eclipses in the space of 18 months for the country. With so much to see, planning will be key.” Jamie is your eclipse guide on page 60 66

“One of the most exciting missions we’ve ever sent to Jupiter is sadly nearing its end. I dug into what Juno has revealed about the gas giant.” Nicky shares Juno’s greatest hits on page 34

Take on the Messier Catalogue marathon

Our extended gallery featuring the best astro images sent to us by BBC Sky at Night Magazine readers.

Download the complete Messier Catalogue to your phone or tablet. How many targets can you tick off the list?

LEGENDS

Two duelling dragons square up for a cosmic clash

VICTOR M BLANCO 4-METER TELESCOPE, 9 JULY 2025

THE STUFF OF T

his is NGC 6188, an emission nebula 4,000 lightyears from Earth, known as the Fighting Dragons of Ara because of its resemblance to two dragons preparing to face off (seen here in close-up). The nebula lies in the constellation of Ara, the Altar, and its reddish glow comes from

ionised hydrogen that’s being illuminated by energetic outflows from the region’s many young stars, no more than a few million years old. The intense stellar wind blasting outwards from these stars has sculpted and shaped the surrounding gas and dust into the striking draconic forms we see today.

 Cluster buster

JAMES WEBB SPACE TELESCOPE, CHANDRA X-RAY OBSERVATORY,

30 JUNE 2025

A new study of the Bullet Cluster is helping to shed light on the behaviour of dark matter. Located in the constellation Carina, the Bullet Cluster is the result of a collision between two galaxy clusters. Webb’s near-infrared view reveals more extremely faint, distant galaxies than ever seen in this region, where the merging clusters are rich in hot gas (pink) and dark matter (blue).

Taurean trio 

HUBBLE SPACE TELESCOPE, 30 JUNE 2025

At the centre of this image are three young stars – HP Tau, G2 and G3 – each less than 10 million years old. They’re nestled within a small part of the Taurus Molecular Cloud, a star-forming region 480 lightyears away in the constellation Taurus. Together, these stellar youngsters illuminate the wispy grey dust clouds of a reflection nebula.

FREE BONUS CONTENT

Explore a gallery of these and more stunning space images www.skyatnightmagazine.com/ bonus-content

Double whammy 

ESO VERY LARGE TELESCOPE, HUBBLE SPACE TELESCOPE,

2 JULY 2025

Supernovae aren’t uncommon in the Universe, but double ones definitely are! This new VLT image of supernova remnant SNR 0509-67.5, with its concentric rings of calcium (blue) and hydrogen (orange), reveals that the deceased star exploded not once but twice, hundreds of years ago. It’s the first double-detonated star ever found.

 Paw visibility

JAMES WEBB SPACE TELESCOPE, 10 JULY 2025

Emission nebula NGC 6334 is known as the Cat’s Paw Nebula due to its resemblance to the pads on a feline foot. Here, Webb zooms in on just one ‘pad’ and reveals that its gas, dust and stars are arranged in further, smaller pad-like structures, uncannily echoing the shape of the wider nebula.

The latest astronomy and space news, written by

Anita Chandran

BULLETIN

 Comet

3I/ATLAS’s inbound path from deep space, captured by the ATLAS telescope in Chile (right) in July

Ancient interstellar object detected

3I/ATLAS could be the oldest comet ever seen

Is it a bird? Is it a plane? No, it’s a mysterious interstellar interloper spotted passing through our Solar System. The comet, named 3I/ATLAS, was discovered by NASA’s Asteroid Terrestrial-impact Last Alert System (ATLAS) survey telescope. Currently 675 million km (420 million miles) away, it could be the oldest comet ever seen.

“Rather than the quiet Wednesday I had planned, I woke up to messages like ‘3I!!!!!!!!!!’,” says Matthew Hopkins, one of the astronomers who discovered the comet. Hopkins and the team developed the Ōtautahi–Oxford model to predict the properties of interstellar objects based on their orbits and possible origins.

Non-interstellar comets, like Halley’s Comet, formed within our Solar System and are no older than the Solar System’s 4.5-billion-year lifespan. Interstellar visitors, however, are not formed around the Sun and can be much older. The team’s modelling suggests 3I/ATLAS is more than seven billion years old – the oldest comet identified to date.

“It’s a fantastic opportunity to test our model on something brand new and possibly ancient,” Hopkins continues.

3I/ATLAS is only the third-known interstellar object to have been observed, following 2I/Borisov in 2019 and ‘Oumuamua in 2017. Unlike its predecessors, it is travelling on a much steeper path through the Galaxy, implying it originated in a completely different region of the Milky Way.

It’s thought the comet formed in the Milky Way’s ‘thick disc’, a region of ancient stars that contains about 10 per cent of our Galaxy’s stellar mass. If it does originate from around an old star in the thick disc, that implies that the comet should be rich in water-ice.

“This is an object from a part of the Galaxy we’ve never seen up close before,” says Professor Chris Lintott, who co-authored the study.

As 3I/ATLAS nears the Sun, its surface will heat up, allowing scientists to observe whether the expulsion of vapour and dust will form a classic glowing tail. As well as having implications for how we detect interstellar comets, astronomers also hope 3I/ATLAS will provide clues about the role of interstellar objects in star and planet formation within our Galaxy. www.science.nasa.gov

by Chris Lintott

Five billion years ago or so, another interstellar object passed through our part of the Galaxy. This wanderer, perhaps similar to 3I/ATLAS, became trapped in the nebula from which the Sun was forming.

Within the disc of material around our newly born star, the object began to accrete material, growing quickly into a more substantial body – one that would become the planet Earth. Is this true?

Astronomers

Suzanne Pfalzner and Michele Bannister proposed this idea following the arrival of ‘Oumuamua, and the romance of it grabbed me immediately. Maybe the arrival of 3I will help us understand whether this idea about our cosmic origins holds up. Chris Lintott co-presents The Sky at Night

TWA 7b, the potential planet around a star just 34 lightyears away – a JWST imaging first, if confirmed

JWST captures possible Saturn-sized exoplanet

The new world may be the first the telescope has discovered by direct imaging

JWST has spotted evidence of a planet lurking in a disc of debris orbiting nearby star TWA 7. The object, known as TWA 7b, could be a young, cold planet with a mass similar to that of Saturn – around 100 times more massive than Earth.

Debris discs orbit both young and old stars and are filled with dust and rocky material. They often contain gaps, thought to be created by planets forming around these stars. However, such a planet has never been discovered before.

“Our observations reveal a strong candidate for a planet shaping the

structure of the TWA 7 debris disc, and its position is exactly where we expected to find a planet of this mass,” says AnneMarie Lagrange, one of the scientists who discovered the potential new world.

Using JWST’s mid-infrared instrument, MIRI, planet-hunters found a faint infrared source in TWA 7’s debris disc. To do this, they suppressed the bright glare of the host star, which means faint nearby objects can be more easily seen.

TWA 7’s disc is also face-on to Earth, which makes it an easier target for JWST to observe.

The infrared source was found in a gap in one the three dust rings within TWA 7’s debris disc, exactly where a planet would be theorised to form. The source’s brightness and colour also match predictions for a young, cold planet.

While there remains a slim chance that TWA 7b is a distant, background galaxy, evidence points towards the object being an undiscovered planet. The observation represents a step forward in our ability to detect exoplanets with similar masses to those of planets in our Solar System. www.webbtelescope.org

Astronomers find Universe’s missing matter

Cosmic radio signals reveal the shadow of material lost in intergalactic space

About 16 per cent of all the Universe’s matter is ‘ordinary’, including everything from atomic nuclei to human beings. Unlike its mysterious counterpart, dark matter, it also emits light and interacts with other matter, meaning that it can – in principle – be detected. Despite this, a significant fraction of ordinary matter has gone unaccounted for, lost in the vast spaces between galaxies. Astronomers have now found it.

The researchers from Caltech and Harvard’s Centre for Astrophysics used fast radio bursts (FRBs) – bright and fleeting flashes of radio-frequency radiation from the distant cosmos – to

illuminate the sparsely spread missing matter.

“The FRBs shine through the fog of the intergalactic medium, and by precisely measuring how the light slows down, we can weigh that fog, even when it’s too faint to see,” says Liam Connor, one of the astronomers at Harvard who worked on the discovery.

As the light from these FRBs travels to Earth, it disperses like sunlight travelling through a prism. The more ordinary (or baryonic) matter is in the way, the more the dispersion. This is because light is being impeded by the particles (baryons) in the matter.

“It’s like we’re seeing the shadow of all the baryons,

Researchers used fast radio bursts to expose diffuse matter hidden between galaxies

with FRBs as the backlight,” says Vikram Ravi, assistant professor of astronomy at Caltech. “If you see a person in front of you, you can find out a

lot about them. But if you just see their shadow, you still know that they’re there and roughly how big they are.” www.caltech.edu

The dwarf nova flared 2,500 times brighter for just a few hours in October 2024

 Multiple telescopes captured GOTO0650 exploding and fading, but it was first identified by Kilonova Seekers volunteers

Citizen scientists catch star exploding in real time

Members of the public spotted the outburst within hours of its detection by telescopes

A citizen astronomy project known as Kilonova Seekers has discovered an exploding star system in real time. Described as like a game of astronomical ‘spot the difference’, the project invites members of the public around the world to compare images of the night sky to images of the same section taken on previous nights. This time, the difference was an extremely bright exploding star.

The explosion caused the star to brighten by a factor of 2,500. The fast response of participants meant that an unusually complete set of observations could then be made, including spectroscopy, X-ray and UV measurements. The wealth of data resulted in the discovery of what’s called a ‘period bouncer’, a type of cataclysmic variable star, now named GOTO0650.

Cataclysmic variable stars fluctuate dramatically and unpredictably in brightness. They are composed of a pair of stars, one being a white dwarf star that steals matter from its orbiting counterpart. Every so often, material from the donor star reaches a critical point in temperature and density, triggering an explosive outburst of energy and bright light.

“Kilonova Seekers is a unique opportunity for members of the public to take part in true real-time astrophysics,” says project co-leader Dr Tom Killestein. “Remarkably, public volunteers identified this star as an object of interest within 3.5 hours of the image being taken by the GOTO telescopes – this discovery could have been missed among many other objects without their efforts.”

This is no exaggeration. The volume of data generated by survey telescopes is massive – and growing rapidly. Soon, the sheer number of images will be too large for small research groups and individuals to label and validate. In these circumstances, citizen science shines, and can prevent important scientific discoveries being missed.

“This discovery was very important to me, as I was going through a serious health problem and the citizen science we do at Kilonova Seekers was distracting me from my situation,” says Cledison Marcos da Silva, a Kilonova Seekers volunteer based in Brazil. “Even from your bed, or on the street with your cellphone, there is the possibility of making a very important discovery.”

www.warwick.ac.uk

First light for Vera Rubin Observatory

New science facility captures cosmic phenomena on unprecedented scales

The Vera C Rubin Observatory has released its first images, capturing millions of galaxies and stars, along with thousands of asteroids. Taken during just 10 hours of test observations, the images mark the culmination of over two decades of work. They show fractions of the night sky in extraordinary definition, but the observatory will soon target a feast of cosmic phenomena, from asteroids and comets to supernovae. Rubin Observatory sits at the summit of Cerro Pachón in Chile, where the combination of dry air and dark, clear skies creates excellent observing conditions. It is named after American astronomer Vera C Rubin, who provided the first compelling evidence for the existence of dark matter, the invisible material that permeates our Universe. Exploring the nature of dark matter and dark energy will be one of the new observatory’s biggest scientific missions. rubinobservatory.org

 Read more in our feature on page 28

The new observatory hopes to lift the lid on the invisible forces shaping the Universe

BULLETIN

Earth may be at the centre of a huge void

New theory could explain why the Universe expands faster in our region of space

It’s human to feel alarmed by the sheer emptiness of space. Now, astronomers from the University of Portsmouth suggest this unsettling vastness may be worse than we thought, claiming that our entire Milky Way sits inside a mysterious giant hole. This void, they believe, may cause the cosmos to expand more quickly in our local environment than in other parts of the Universe.

The void idea was proposed as a way of solving what’s known as the Hubble tension (or the Hubble crisis), a conundrum that has puzzled astronomers for years. The tension refers to the fact that the rate of the expansion of the Universe varies depending on where it’s measured. This discrepancy is a major problem for cosmologists, who need to know the expansion rate to accurately determine the Universe’s age.

We (the green dot) may be adrift in a giant cosmic void, with matter flowing away into denser regions beyond

“A potential solution to this inconsistency is that our Galaxy is close to the centre of a large, local void,” explains Dr Indranil Banik, who recently proposed the idea at an astronomy conference in Durham. Banik presented data examining baryon acoustic oscillations (BAOs)

Ice in space isn’t so alien after all

– which roughly translate as the ‘sound’ of the Big Bang. The findings showed that a void model is about 100 million times more likely than a void-free model.

For this theory to hold, Earth and our local galactic neighbourhood would need to lie near the centre of a void around a billion lightyears in radius, with a density about 20 per cent lower than the Universe’s average.

But the idea of voids is controversial within the cosmology community. The standard cosmological model instead suggests that matter should be more uniformly spread throughout the Universe. While the answer hasn’t been definitively found, evidence for the void model could help cosmologists advance our understanding of the Universe’s structure. www.ras.ac.uk

Findings challenge the idea that life on Earth was seeded from elsewhere

For decades, scientists believed that ice in space is very different to ice on Earth. Here, ice is crystalline, its molecules being highly ordered, while it was thought that space ice was the opposite, with a completely disordered or ‘amorphous’ structure. Now, scientists have discovered that space ice might have some crystalline structure after all. Previously, the cold temperatures of space were thought to prevent ice from forming crystals – there simply wasn’t enough energy to do so. But by using computer simulations on the most common form of ice in the Universe – found in comets, on icy moons and in dust clouds – scientists found that space ice was not fully disordered, and

 Space ice isn’t as disordered as thought: it contains tiny crystals, much like Earth ice

instead is embedded with tiny crystals, just slightly wider than a strand of DNA.

“We now have a good idea of what the most common form of ice in the Universe

looks like at an atomic level,” says Michael Davies, the lead scientist working on the discovery. “This is important, as ice is involved in many cosmological processes – for instance, in how planets form, how galaxies evolve, and how matter moves around the Universe.”

This could challenge the theory of Panspermia, which suggests the building blocks of life were carried to Earth on an ice comet. “Our findings suggest this ice would be a less good transport material for these origin-oflife molecules. That’s because a partly crystalline structure has less space in which these ingredients could become embedded.” www.ucl.ac.uk

Starburst galaxy outshines

Milky Way

JWST image of galaxy Messier 82 reveals a flurry of star formation

The JWST has captured a nearby galaxy that is outshining the Milky Way. Messier 82 (M82), known as the Cigar Galaxy, lies just 12 million lightyears away and is classified as a starburst galaxy, one in which new stars form at a much faster rate than expected. The new image, taken with JWST’s near-infrared camera

(NIRCam), shows the luminous flare of billions of stars, as well as the glow of organic molecules called polycyclic aromatic hydrocarbons.

The burst of star formation in M82 is likely due to its neighbour, spiral galaxy M81. Astronomers believe gravitational interactions between the two sent large

JWST’s infrared eye on M82 shows a galaxy in full-blown star-making overdrive

amounts of gas hurtling into M82’s centre millions of years ago, which caused a flurry of new stars to form.

M82 is now home to over 100 super star clusters – more massive and luminous than other clusters – each containing hundreds of thousands of stars. www.esawebb.org

Our experts examine the hottest new research

CUTTING EDGE

Saturn’s ring has space rainbows

Water-ice spouting from moon Enceladus is creating peculiar striped bands of light in Saturn’s E ring

One of the Cassini orbiter’s stand-out discoveries in the Saturn system was plumes of water-ice erupting from fissures in the moon Enceladus. These ice particles make up the diffuse E ring surrounding Saturn. Now, a team fronted by Niels Rubbrecht, at the Delft University of Technology in the Netherlands, has found something just as unique created by Enceladus’s icy eruptions.

Rubbrecht and his colleagues were looking through old photos captured by Cassini during its 17th close fly-by of Enceladus on 27 March 2012. They spotted distinct stripe-like features appearing around the moon in images taken by both the Visual and Infrared Mapping Spectrometer (VIMS) and the visible Narrow-Angle Camera (NAC) on the probe. The team went back through other Cassini images taken under similar lighting conditions, including fly-bys of other moons such as Titan, Dione, Phoebe and Tethys. But stripes were only apparent in two other Enceladus fly-bys, in December 2010 and May 2012. The relative positions of these parallel stripes were consistent between different images – angled around 16° to the plane of the Solar System (or 43° out of the plane of Saturn’s rings) – so they’re

definitely a real effect and not stray light in the camera lens. And the fact that these observations span almost a year and a half suggests that this curious phenomenon persists for at least that time.

Tellingly, the separate bands making up the stripes appear to shift in position slightly when examined in different wavelengths of light; this gave the team a big clue as to what’s behind this “light-dispersing phenomenon”. Rainbows on Earth are created when sunlight reflects off the back of raindrops, with refraction occurring as the rays pass from the air to water and back out again, splitting the white light into a visible spectrum of colours. The physics in the vacuum around Saturn’s rings is slightly different, but it’s creating a similar effect. Sunlight reflecting straight off ice crystals produces the brightest band seen in the Cassini images, with a wavelength of around 5μm. But because the ice particles are so tiny, they create what’s known as a reflection grating, diffracting the light and spreading it into its component wavelengths.

Plumes seed the stripes

The fact that these stripes are only visible near Enceladus suggests the reflection grating is probably made up of the particles spewing out of the moon’s plumes.

“The bands appear to shift when examined in different wavelengths; this gave the team a big clue as to what’s behind this phenomenon”

Prof Lewis Dartnell is an astrobiologist at the University of Westminster

The spectrum of the bright band produced by VIMS indicates that it’s caused by water-ice crystals with a smattering of carbon dioxide ice, which suggests the material has been freshly ejected into space. However, the researchers aren’t yet entirely clear why these particles are larger than those in the plumes, and are inclined so far out of Saturn’s rings. They note that optical phenomena common in Earth’s atmosphere have also been discovered in other worlds. In 2014, the Venus Express orbiter spotted a ring of refracted sunlight known as a halo on the Venusian upper cloud layer. And the same effect has been observed by the Perseverance rover, created by hexagonal-shaped ice crystals in Martian clouds. But this particular discovery is unprecedented, and has a wonderful poetic beauty to it: the fountains of Enceladus are creating space rainbows.

Lewis Dartnell was reading… Peculiar Rainbows in Saturn’s E Ring: Uncovering Luminous Bands near Enceladus by Niels Rubbrecht, Stéphanie Cazaux et al. Read it online at: arxiv.org/abs/2502.18028

Multi-filter Cassini images show the plumes scattering light into faint stripes

a) IR3

b) IR3

Clear IR1 Red BL1

Lone black holes may finally break cover

These hidden drifters could reveal themselves through a telltale flicker

Flicking through the pages of BBC Sky at Night Magazine each month, you’d be forgiven for thinking astronomers have black holes pinned down. Whether it’s the dramatic imaging of black hole shadows by the Event Horizon Telescope, observations of gravitational waves with magnificent instruments such as LIGO, or the discovery of actively growing black holes in images taken by the JWST of the early Universe, we’ve never had more ways to observe and understand these elusive and fascinating beasts.

Prof

Chris Lintott is an astrophysicist and co-presenter on The Sky at Night

“Because accretion discs around such black holes can change very fast, we should expect any such source to flicker rapidly”

Yet most still escape our gaze. The most common type of black hole is probably that produced by the death of a single massive star, left to wander the galaxy alone; there may be 100 million of these things in the Milky Way alone. While black holes in binary systems can be detected by their effects on companions, only one of these isolated black holes has ever been spotted, detected as light from a background star was bent – gravitationally lensed – by its passage.

Lena Murchikova and Kailash Sahu, the authors of this month’s research paper, have a plan to change that. They take as their starting point the realisation that we should have plenty of local black holes: something like 35 within 150 lightyears of us. Black holes, of course, notoriously do not emit light, but when material accretes onto them it can form a bright disc, converting gravitational energy into light that we can detect.

A matter of density

So, will any of these black holes be consuming matter at a high enough rate that we might see them? The calculations in the paper, building on physics developed in the 1950s by Hermann Bondi in Cambridge, show that black holes passing through the densest clumps of gas and dust in our local interstellar medium would shine brightly enough to be easily seen with our most advanced telescopes, provided we look in the right place at the right time.

Such clumps account for just a small fraction of our surroundings, though, and the odds of a black hole ending up in one, just when we have produced telescopes powerful enough to see it, are low. More promising is the predicted emission from a black hole passing through a feature called the Local Interstellar Cloud, a dense region of gas and dust through which our Solar System is currently moving. An object here would accrete enough material to be observed by our best telescopes with a few hours of effort, if we knew where it was.

This is where the authors make a really smart suggestion: because accretion discs around such black holes will be small, they can change very fast. We should expect any such source to flicker rapidly – on millisecond timescales – more or less randomly, as well as displaying longerterm variability. If we could look for sources that change that quickly, we might be able to pick out our local single black holes from all the other things that change in the sky.

The Vera C Rubin Observatory in Chile (see page 28), which is just starting to map the sky, should spot things changing as fast as every 15 seconds. If this research paper’s calculations hold up, that might just be enough to catch our nearest black holes, hidden no more in the darkness of deep space.

Read it online at: arxiv.org/abs/2506.20711

Chris Lintott was reading… Observability of Isolated Stellar-mass Black Holes by Lena Murchikova and Kailash Sahu

A clever new method could expose nearby black holes that have long evaded detection

Behind the scenes of The Sky at Night TV show

INSIDE THE SKY AT NIGHT

August’s episode of The Sky at Night celebrates the work of Jocelyn Bell Burnell. George Dransfield explains why this pulsar pioneer is such a hero to her

Ihad one answer, every time: Jocelyn Bell Burnell. Whenever Amaury Triaud, my PhD supervisor, asked for speaker suggestions for our weekly seminars, hers was the name I suggested. Again and again. He’d patiently remind me that it might be tough to get her in, seeing as she’s a living legend and all, but still I asked.

Finally, in October 2021, the day came when he told me that Professor Dame Jocelyn Bell Burnell would be coming to Birmingham and doing a meet and greet. “But there’s a catch,” he said.

“The only slot she can do is in February.”

“This coming February?”

“That’s right. If you want to attend the talk and meet Jocelyn, you will have to cancel your trip to Antarctica.”

I’ll be honest, I briefly hesitated. And right now, at the time of writing, I still haven’t met the great JBB, despite us having offices on the same floor of the same building in Oxford. If you’d seen me positively

George Dransfield is an exoplanet huntress at the University of Oxford and a presenter on The Sky at Night

sobbing at a Michael Bolton concert in 2013, you’d understand: I slightly lose my cool in the presence of those I admire, and I really don’t want to make a boob of myself in front of the one and only Jocelyn Bell Burnell

So, why the endless fascination with the woman who discovered pulsars, those incredibly dense, rapidly rotating neutron stars? To be clear, I don’t feel the same way about the person who discovered, say, quasars. That’s because Bell Burnell’s story isn’t just about her incredible scientific achievements – it’s about what she represents to all of us who have ever felt like outsiders in science.

“It’s about what she represents to all of us who have ever felt like outsiders in science”

George is starstruck by Jocelyn Bell Burnell, who discovered pulsars but was denied the Nobel Prize

The Sky at Night wants your questions

For one special episode coming later this autumn, The Sky at Night is joining forces with the hit Radio 4 series Curious Cases to examine space mysteries sent in by you, the audience! If there’s an intergalactic mystery you’ve always wanted an answer to, the team want to hear about it. Just email your question to curiouscases@bbc.co.uk and our expert presenters will get on the case.

Be in the audience

The Sky at Night’s special episode with Curious Cases will be filmed in front of a live studio audience on 13 October 2025, in London. Audience tickets can be applied for at www.bbc.co.uk/showsandtours from early September.

August’s episode of The Sky at Night celebrates this powerhouse of a scientist. You’ll hear all about how she spent ages poring over metres – actual lengths of paper! – of data as a PhD student and spotted some unusual signals. Jocelyn had a hunch and she followed it up tenaciously, even when her PhD supervisor told her it was nothing. As a result, he got a Nobel Prize for the discovery of pulsars. Jocelyn Bell Burnell did not get to share this accolade.

Credit where it’s due

Science research students everywhere can relate to the thrill of finding ‘something strange’. We check a hundred times that it’s not just a mistake. Then we nervously show it to our supervisors – and most often get told it’s likely nothing. But we investigate it anyway, because we are scientists. Young and inexperienced, maybe, but scientists nonetheless, with real data to play with. And the payoff when we turn out to be right should be, at the very least, credit for the discovery.

Bell Burnell’s Nobel snub has mythical status in astronomy, and while it’s never been acknowledged as such, it’s widely believed that her gender was the key factor. Again, so very relatable, because it’s hard convincing yourself you belong when you don’t look like… most Nobel Prize winners.

But as you’ll learn in this month’s episode, Bell Burnell is made of noble stuff. Beyond inspiring the

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next generation of scientists, she is actively helping those from underrepresented groups to pursue their careers. A beloved friend of mine is a Bell Burnell Scholar. She’s the first in her family to attend university and, thanks to Bell Burnell’s scholarship fund, can afford her commute while pursuing her PhD.

Far be it from me to bring everything back to exoplanets, but the first planets discovered beyond the Solar System orbit a pulsar – so Bell Burnell’s work also paved the way for countless more discoveries in a whole other field of astronomy.

I guess the only thing left to be seen is whether anyone lets me near JBB during filming in the coming weeks. And if they do, will I keep it together? You’ll have to tune in to find out!

SEPTEMBER

Big Bang and beyond: the TV team tackle the expansion question

As a PhD student in 1968, proving that sometimes a hunch is everything

The Expanding Universe

Edwin Hubble’s discovery in the 1920s that the Universe is expanding was a landmark moment in science, leading to the idea that the cosmos emerged from the Big Bang. In this episode, The Sky at Night team explore how astronomers are probing cosmic expansion and how powerful observatories are getting us closer to solving its greatest mysteries.

Four, 8 September, 10pm (first repeat will be on Four, 11 September 00:40am) Check www.bbc.co.uk/skyatnight for more up-to-date information

warmest welcome at sea

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Emails – Letters – Tweets – Instagram

INTERACTIVE

Smartphone meets Uranus

This is my photo (right) taken on 27 June 2025 at 03:46 MST, just two minutes before astronomical twilight, the very start of early dawn. It shows the Pleiades star cluster rising over the Tucson Mountains. What’s most exciting is that lone sixth-magnitude ‘star’ closest to the ridgeline on the far right of frame: it’s the planet Uranus!

I’ve viewed Uranus through my 8-inch Celestron many times, but photographing it is hard. It was completely invisible to the naked eye under these (albeit early) twilight conditions. I used an Android Pixel 8 Pro smartphone mounted on a tripod, with 5x magnification and a three-second exposure in Night Sight mode, an ISO

Tweet

Andrew S-W

@Andrew_SW • 22 June

around 1000, and a remote shutter release. I calculated that Uranus would crest the ridge at 03:36 MST and snapped my photo just 10 minutes later when the planet had risen, very nearly along the ecliptic, about 2.5° above the horizon.

With perfect timing and just a Pixel phone, Gordon captured Uranus – 3 billion km away!

The sky was already brightening so rapidly that I had to use my 11x80 binoculars to even find the Pleiades, after which I pointed my camera in its vicinity. Before going to bed, I’d plotted Uranus’s position on my star atlas; that object just a little above the mountain range is, indeed, the second-mostdistant planet in our Solar System (Neptune being the farthest). It is quite a picturesque capture, allowing each of the brightest stars in the tight cluster to stand out vividly.

Something I’ve been meaning to do for ages, and finally did it! The centre of the #milkyway over #durdledoor. With no light pollution, the view of the summer #nightsky was spectacular. #Dorset @skyatnightmag

Lucky streak

While going through my photos, I came across one you might be interested in (above). I have no idea what the object is, and would love to find out. This was taken on 6 April 2025 at 21:01 BST from Goringby-Sea, West Sussex, using a Samsung S25 Ultra (ISO 3200, 0.5-second exposure at f/1.7). The object was moving very quickly across the field of view, crossing M37 and Alhena and leaving a visible trail. When zoomed in, the rear of the object looks very bright.

Greg Master, via email

Gordon Moyer, Tucson, Arizona

Congratulations on capturing Uranus, Gordon! From your image, it’s clear how much fainter the planet is than the Pleiades on this challenging occasion. – Ed.

Surprise fly-by

Whilst in my garden with my dog, between 01:00 and 01:10 on the morning of 11 July, looking at the sky for planets, a brightly lit object seemed to come from nowhere. I watched it until it disappeared – a matter of minutes, if that. There was no noise coming from it. I’m positive it was the International Space Station and I’m beyond thrilled to have seen it.

Anne Corrigan, Falkland, Fife

Farewell, Big John

Here’s a wee ditty about my favourite 12-inch Dobsonian telescope that I sold recently, and which I miss dearly! Ode to ‘Big John’ (John Dobson) I saw some epic sights with you, Vega shone like crystal blue, Jupiter’s belts were an awesome sight, The Great Double Cluster set the eyepiece alight!

Orion’s nebula just can’t be beat, 

Greg’s shot of a mystery zoomer over West Sussex

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While Saturn is the best astronomy treat. I’ll miss you Big John and the stuff you did track, But I’m getting old and so is my back! David Millar, Abernethy, Perth & Kinross

Planet 9 found! …And lost again

Now you see it…

I don’t get this. In your Cutting Edge article, ‘Signs point to Planet 9’ (July issue), you say there’s a lack of evidence for a Planet 9, yet on this star map (above) someone has both identified and located it. I took this screenshot from the Star Walk 2 app on my phone in 2016. Can someone explain this to me?

Michael Surface, via email

How intriguing, Michael! It seems that in 2016, after Konstantin Batygin and Mike Brown proposed a possible orbit for Planet 9, the Star Walk 2 creators got in touch with them to include its ephemerides in the app. With no direct evidence since, it’s been removed from Star Walk 2. But who knows? It could reappear in all star-finding apps one day! – Ed.

SOCIETY IN FOCUS

Galloway Forest Astronomical Society (GFAS) recently held its first-ever ‘Zoomin’ events, bring expert astronomers together with GFAS members and the wider public in rural southwest Scotland.

In April, Royal Observatory Greenwich’s Astronomer Emeritus Brendan Owens gave a terrific talk on the exploration of Mars. Then in early May, renowned astrophotographer, author and artist Mary McIntyre gave a talk about the constellations in our night sky, and the myths and legends connected with them.

GFAS is a registered Scottish charity with an active outreach programme and a mission to promote astronomy. We take our inflatable planetarium to primary and secondary schools and community centres in the area, bringing the wonders of the night sky to children and adults alike. We also run daytime solar-viewing events, as well as nighttime observing

riacardo.ad.santos • 10 July I tested something I’ve been wanting to do for a while: capturing a moontrail. For a 15-minute exposure, I had to lower the aperture as much as possible and use my ND1000 filter to avoid over-exposing the Moon. The foreground comes from a photo I took during a visit to the Berlengas. Both parts of the image were taken at 200mm. @bbcskyatnightmag

Joint effort

Jane Green’s ‘Chandra: uncovering the high-energy Universe’ (July issue) was great, with some amazing images. It was nice to see an article that details the collaborative workings of the different types of analysis, and how much more the images can convey when combined so beautifully. Thank you!

Samina Ghafoor, via email

 GFAS members gathered in hope of catching March’s partial solar eclipse

sessions. The weather can be a bit of a challenge here: our partial solar eclipse session in March was completely clouded out, but at our summer solstice event we were all able to observe two excellent groups of sunspots.

For our July meeting, we organised with the Newton Stewart Cinema to see the greatest sci-fi film of all time, 2001: A Space Odyssey, on the big screen. Andy Sawers, GFAS treasurer  @gfastro on Facebook

The astronomer’s forum

FIELD OF VIEW

One sky – then, now and forever

The starry sky is the one unchanged view we share with our ancestors, says Mark Westmoquette. It’s our link to every soul who ever paused to wonder

Author

of The

Mindful Universe, astronomer and mindfulness

teacher Mark Westmoquette lives with his young family in London and can be reached at www.markwest moquette.co.uk

Imagine an early human out on the savannah, stepping away from the evening fire, glancing up at the dark sky and being totally captivated by the tiny, twinkling sparks dotted everywhere. Eyes wide, head tilted, and just the sound of his or her own quiet breathing and the crackling of the fire.

Since the dawn of homo sapiens around 300,000 years ago, every other view of our planet has changed – mountains have been eroded, sea levels have risen and fallen, volcanoes and earthquakes have reshaped the land, and swamps have been drained. The only view that has stayed more or less the same is the night sky (the patterns of stars will have changed only slightly over that time due to proper motion). It blows my mind every time I identify a constellation and realise that I’m sharing that view with all our Northern Hemisphere ancestors going back through hundreds of millennia, whether they lived on the savannah, mountains or coasts.

There’s evidence that shows people of the past may even have seen some of the same shapes in the star patterns we’re familiar with today. The oldest star chart we know of is over 32,000 years old, etched

into a sliver of mammoth tusk found in 1979 in a cave in Germany. It shows a constellation that looks remarkably like Orion. And it’s thought that markings in the Lascaux cave paintings in France, dating back at least 17,000 years, depict parts of the constellation Taurus.

The night sky is as beautiful, mysterious and awe-inspiring to us modern humans as it has been to any animal that has ever had the capability of looking up and wondering.

But as astronomers, it’s easy to get so trapped in a layer of intellectual knowledge that we stop actually seeing stars – we just see facts, coordinates and pointers to deep-sky objects. That’s certainly what happened to me. Years of astrophysical study and research gradually eroded my sense of the raw beauty of the night sky, as feelings and wonder got replaced by facts and intellectual knowledge. That was to my detriment – I lived in a detached, rather greyed-out world of thoughts and facts about nature, rather than a full-colour world of direct experience and beauty.

For me, it took a decision to leave professional astronomy and reorient my life towards a more embodied and mindful way of living, to begin reconnecting to the magic and wonder of the night sky. Eventually, it was a move to the very dark island of Saint Helena in the South Atlantic that fully rekindled my joy in simply gazing at the stars. But I’m not suggesting everyone needs to do that! All it takes is a change of ‘camera lens’, as it were.

How would it be to gaze at the starry sky as if you were looking at a wonderful piece of art, remembering that all of humanity through time has shared this same view? Gazing is the right word here: it conveys a sense of drinking in the view with wide-open senses. Not throwing out the facts and science entirely – they add more wonder and awe – but considering them only once we’ve made that direct connection with the timeless beauty of the night sky.

The perfect addition to your stargazing, BBC Sky at Night Magazine is your practical guide to astronomy, helping you to discover the night skies, understand the Universe around us and learn exciting techniques for using your telescope.

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Observatory Vera C Rubin Inside the

The brand-new observatory is about to begin its 10-year survey of the night sky. KR Callaway visited the facility to find out how it will shed light on the Universe’s darkest mysteries

Driving up dusty mountain roads flanked by cacti and colourful bursts of wildflowers, it’s hard to imagine these quiet peaks in the Chilean Andes are home to some of the most sophisticated astronomical instruments on Earth. Atop Cerro Pachón, 2,715 metres (8,900ft) above sea level, the newly constructed Vera C Rubin Observatory is ready to reshape our understanding of the cosmos. Its 10-year Legacy Survey of Space and Time (LSST) is slated to start later this year.

Visiting the facility in May, it was a marvel to see the telescope whirring to life. Gathered on a platform inside the dome with scientists and other visitors, I watched as the massive teal-coloured structure rotated and angled towards the sky. We were seeing it move at only a fraction of its maximum speed, but it was already fast and fluid, gliding between positions. At full speed, the telescope will complete scans of the entire Southern Hemisphere sky in just three or four nights, collecting thousands of detailed pictures with its 3,200-megapixel digital camera, the world’s largest.

A new era of sky watching – Rubin will map the most ambitious 3D time-lapse of the Universe ever attempted

 Vera Rubin, whose work offered early evidence for dark matter, lends her name to the observatory

The camera’s first images, released in June, were a preview of what to expect from the decade-long LSST survey. One, a widefield view of the southern Virgo Cluster called the Cosmic Treasure Chest, looked deeply into just a small percentage of what Rubin can see. It revealed a startling level of clarity, with around 10 million galaxies springing forth in rich detail.

“Any image is very exciting,” says Vincent Riot, former LSST Camera project manager. “It basically means that everything works.” But Riot admits he is even more excited to see data released after the survey starts. Yet more comprehensive images covering wider fields of view will emerge as the telescope traces the sky night after night, creating a dynamic portrait of the Universe.

A telescope with a mission

Named after the late American astronomer Vera Rubin (1928–2016), whose research on galaxy rotation yielded the first solid evidence for dark matter, the observatory started as an idea for a dark matter telescope in the early 1990s. Scientists wanted to create an optical system that could see galaxies near and far, giving us a better understanding of how dark matter and dark energy guide their structure and arrangement. However, creating a telescope with such a sensitive optical system and wide field of view meant it would be capable of much more than looking for the unseen.

“We knew that if we were going to be successful, we had to cover a broad range of science,” says Željko Ivezić, director of the observatory.

Looking for faint, faraway galaxies also holds lessons about their formation. Large galaxies like our own are thought to be the product of many smaller galaxies merging. Rubin’s intricate optical system

is expected to pick up on faint remnants of these mergers and other signs of the Milky Way’s evolution.

In addition to creating the deep, composite images that make seeing faint objects possible, repeatedly photographing each area of the night sky enables Rubin to track any changes that occur, such as asteroids moving through the Solar System, bright supernovae explosions and other objects that change position or brightness over time. It took careful planning and a unique design to create an instrument powerful enough to address all these science goals with the same dataset. “You start with some high-level science goals, and then you trickle that down into the various subsystems,” explains Kevin Fanning, commissioning scientist and member of the camera project team.

Scientists in dozens of countries helped plan and build the observatory’s highly customised instruments and software, beginning in the late 2000s. Then, piece by piece, everything from the

The Cosmic Treasure Chest shows 10 million galaxies, just a taste of the 10 billion Rubin will chart over the next decade

 Telescope components, like the huge 8.4-metre mirror shown here, had to be carefully transported up Cerro Pachón mountain

 The telescope is designed for speed and precision, capturing around 1,000 images a night and scanning the entire Southern sky every three nights

These particles – photons – first strike the telescope’s primary mirror. At 8.4 metres (27.5ft) in diameter, it is one of the largest telescope mirrors ever produced as a single piece of glass. Its large size means it will be able to capture an immense amount of light, including from very faint and distant galaxies. The mirror was cast in Arizona by heating glass at temperatures over 1,000°C (1,800ºF) on a mould placed within a spinning oven. Then, after months of careful preparation, polishing and additional testing, it was transported by ship to Chile, where it was coated with silver on site.

Built for speed

 The primary mirror, pictured in the on-site silvercoating chamber 

telescope’s mirrors to the camera itself was carefully transported – often thousands of miles – to the summit of Cerro Pachón. Now fully assembled, the observatory is able to quickly and precisely turn particles of light from distant celestial objects into processed data.

From the primary mirror, photons bounce to the telescope’s 3.5-metre (11.5ft) secondary mirror – one of the largest convex mirrors ever made – and then back down to a tertiary mirror embedded in the primary. Because its first and third mirrors are combined into a single structure, Rubin is much smaller than a telescope with similar capabilities and three separate mirrors might be. This compact silhouette also means the telescope can move fast, an essential feature considering it is expected to

Taming a data mountain

The sheer volume of information Rubin will gather demands a completely new approach

Every time the Rubin camera captures a new patch of sky, it generates a fresh stream of data about the Universe. While this will be a massive treasure trove for astronomical research, handling it poses a unique challenge.

Previous astronomical surveys, such as the Sloan Digital Sky Survey, used software designed for large datasets, but nothing on the scale that Rubin

demands. With a 3,200-megapixel image captured roughly every 30 seconds, the observatory will generate about 20 terabytes of data a night, requiring a complete rethink of how astronomical data is handled.

“It was a giant effort over a decade,” says Ivezić. The key lies in its modular design. The camera has 189 sensors, each of which splits its image data into 16

parts when it’s time to read out the data. Because these segments are processed in parallel, the camera can read out the entire image in about two seconds. Once out of the camera, this data – too large to be downloaded by individual scientists – is stored online and in the cloud, relying on advances in storage and bandwidth that didn’t exist when the observatory was first conceived.

The camera’s 189 sensors split each image into smaller segments for rapid processing

At the summit control room, teams oversee the flow of Rubin’s massive data stream

Cosmic Abundance: part of a Southern sky Rubin will return to night after night, building a dynamic portrait of the Universe

catalogue the entire Southern Hemisphere sky a thousand times over by the end of its 10-year survey.

After passing these mirrors, the photons finally enter the LSST Camera. Weighing 2,800kg (6,170 pounds) and roughly the size of a small car, it’s a colossus. When visiting the dome, you might expect it to be easy to spot, but it is so well integrated into the telescope that you can only catch glimpses of it at certain angles. Inside the camera are three lenses and a rotating carousel of filters that together focus light towards its image sensors and add colour to the pictures it creates.

The heart of the LSST Camera is its focal plane, a 64cm-wide (25-inch) array made up of 189 individual sensors placed just half a millimetre (0.02 inches) apart. Each sensor acts as a little eye for the camera,

collecting its own portion of the image data. And it’s a lot of data: every image taken by Rubin’s camera has a resolution of 3,200 megapixels – 260 times that of a modern smartphone camera – and covers an area of the sky equivalent to about 45 full Moons. Displaying all the data from a single Rubin camera image would require 400 high-definition televisions. The images start their data-processing journey by first travelling through a tangle of wires to an inhouse data centre below the camera. After an initial analysis, they follow a dedicated undersea fibreoptic cable from Cerro Pachón to SLAC in California. There, they will be compared to past pictures taken in the same direction, spotting changes in the night sky and sending out automatic alerts – anywhere between one and 10 million each night – to the

 Left: Rubin’s 3.5-metre secondary mirror directs light from the primary onto the massive camera

Right: the LSST Camera mounted in the observatory is the world’s largest digital camera, with a 3,200-megapixel sensor. For comparison, the iPhone 16 Pro has a 48-megapixel camera

With an exceptionally large field of view, Rubin catches sweeping nebulae scenes in a single frame

science community. Finally, Rubin’s images will join an extensive database that scientists can turn to to unravel the Universe’s many mysteries.

Poised to rewrite astronomy

KR Callaway is a freelance journalist and editor specialising in science, health, history and policy

Creating the cutting-edge equipment that makes this process possible took nearly 30 years, from the first sketches of the proposed dark matter telescope in 1996 to first light earlier this year. Every scientist involved in the project seems to have a differing opinion on which part of the process posed the greatest challenge, but past difficulties only add to their pride in the finished product.

“This is a very challenging project, because our goals are very ambitious,” says Aaron Roodman, deputy director at the observatory. “We have pushed what is possible to the limit, in many different directions, to achieve those goals.”

Q&A with Alan Strauss

Expanding the realm of possibility with stateof-the-art optics and software systems, Rubin promises to generate much more data than any observatory before it –approximately 20 terabytes (20,000 gigabytes) per night. And unlike many observatories, which allocate time to astronomers pursuing specific research goals, Rubin’s survey will produce a large, uniform dataset available to researchers across many areas of astronomy.

Even before data collection for the survey officially begins later this year, excitement has been building both atop the summit and around the world.

Thousands of people across six continents tuned in to see the unveiling of the observatory’s first images. While impressive, these are just the opening few frames of what observatory scientists are calling a time-lapse movie of our Universe.

“I was in the control room when we took the first image,” says Alexandre Boucaud, a software engineer at the French National Centre for Scientific Research (CNRS). “It felt like a great achievement – but five minutes later, it felt like just the beginning.”

The reporting for this article was partially supported by a grant from the US National Science Foundation

Rubin Observatory’s outreach lead on why the science belongs to everyone

What is Vera C Rubin Observatory’s education and public outreach programme?

Data from the observatory’s cuttingedge equipment will be available to everyone, from researchers at elite universities to citizen scientists and even school children. It’s all part of the observatory’s public outreach initiative, an effort to bring more people into the discovery process.

To my knowledge, this is the first time that the US government has funded education and outreach as part of the construction and operation of an observatory.

Long before it took its first images, Rubin’s nascent outreach team came together to envision the many audiences the observatory could serve: the scienceinterested general public, teachers and their students, researchers in the Rubin science community, and citizen scientists who want to volunteer their time to analysing data.

Why is connecting with the public crucial, even before the survey begins?

We want people to get excited about this. Rubin is a unique project in the way data is being provided to every US astronomer, every Chilean astronomer, and other data rights holders.

Some initiatives, such as workshops for teachers and astronomy-related citizen science projects, are already available. And as survey data becomes available, there will be more ways for people interested in Rubin’s science to get involved.

The mission that rewrote the story of Jupiter JUNO

As

NASA’s Juno mission nears its end,

Nicky Jenner explores the secrets it has uncovered about the Solar System’s largest and most enigmatic world

It’s difficult to fully grasp the enormity and extremity of Jupiter. The planet – a striped behemoth of swirling gas with around 100 moons, one of which is larger than Mercury – dominates the Solar System, flooding space with its magnetism and exerting its powerful gravity over everything nearby. The planet contains most of the ‘stuff’ left over after the birth of the Sun, and is so influential that it’s played a central role in shaping our patch of space into the system we see today.

It’s no wonder that we’ve had Jupiter firmly in our sights from our earliest forays into space exploration. We first sent spacecraft there in the 1970s with NASA’s Pioneer and Voyager probes, which swung past the planet and observed it from space. NASA’s Galileo probe stayed a little

longer, taking up residence around Jupiter from 1995 to 2003, and was shortly succeeded by another NASA orbiter that’s still peering down at the gas giant today: Juno.

A gift to Jupiter fans

“NASA sends a probe to deep space – that is, beyond Mars – every decade. Juno was selected for this in 2005,” says Juno scientist John Leif Jørgensen of the Technical University of Denmark. “Previous probes had only been transitory or orbited Jupiter’s equator, offering very limited views of high latitudes. But higher latitudes contain much more information about a planet’s morphology, surface and interior, so we proposed a polar orbiter.”

Such an orbit is subject to harsher radiation and is more complex to operate – but it’s been worth it. “With Juno, practically all

Juno and the Giant: the intrepid spacecraft has spent nine years peering beneath the clouds of the Solar System’s king

possible observations have become superior to those offered by any other mission.”

From its vantage point skimming over Jupiter’s poles, Juno is working to solve the mystery of how the planet formed and has evolved in the billions of years since. Following its arrival at Jupiter in 2016, the spacecraft has dug beneath the planet’s obscuring clouds, investigated its core, studied its striking aurorae and raging storms, and mapped its magnetic field. It’s explored the structures, materials and movements we see in the atmosphere, and looked at how Jupiter’s moons (particularly the largest four) interact with the planet and its wider environment, bringing all of this together to paint a clearer picture of Jupiter’s history – and, by extension, that of our Solar System.

“Juno’s impact on our science is almost immeasurable,” says planetary astronomer Tom Stallard of Northumbria University, who has dug into the upper atmospheres of the gas giants for decades, via missions such as Cassini and the James Webb Space Telescope. “It has profoundly shaped our modern understanding of Jupiter and its near-space environment.”

Finding weird weather

So, what has Juno revealed about Jupiter? First, there’s the weird weather. Juno has spotted violent lightning and electrical storms raging on Jupiter. Unlike lightning storms found here on Earth, which involve water-laden clouds, Jupiter’s are tied to clouds of ammonia, and sling water-ice crystals and slushy, ammonia-rich hailstones – ‘mushballs’ – down into Jupiter’s atmosphere. As these storms need liquid water, we thought they sprang to life deep within large water clouds; however, Juno has revealed that they actually rage far higher up, where temperatures hover at around –88°C (–126°F). Here, ammonia acts a bit like an antifreeze, enabling water to stay liquid, form droplets and support huge storms that electrify and illuminate the swirling cloud tops. Juno has also spied short-lived flashes of light known as ‘sprites’ and ‘elves’ in Jupiter’s upper

atmosphere (sparked by lightning discharging energy in rapid millisecond-long bursts). And it’s dug down to the roots of the famous Great Red Spot, finding this colossal storm extends down for around 300km (185 miles). Jupiter’s bands of eastward and westward winds – which move at different speeds and are expressed as Jupiter’s characteristic caramel-toned stripes – also slice surprisingly far down into the planet. Jet streams seen by Juno at the cloud tops are still blowing 3,000km (1,800 miles) deeper down. Then there’s the cyclones. Thanks to its unique orbit, Juno snapped the first clear views of Jupiter’s poles, showing enduring clusters of whirling cyclones many thousands of miles across – some larger than Australia. Juno initially spotted six at the south pole and nine at the north, arranged in a flower-like pattern with one central cyclone and numerous stormy ‘petals’, before watching a smaller seventh cyclone form at the south pole in 2019. According to Juno’s measurements, these windstorms rage at an intense 360km/h (225mph), not dissimilar to the most extreme tropical cyclones on Earth.

 Juno spotted lightning flashes near Jupiter’s north pole, later revealed to come from high-altitude ammonia clouds

 Left to right: Pioneer 10 gave us our first close-up of Jupiter in 1973; Voyager 2 captured the Great Red Spot in stunning detail in 1979; and Galileo observed the faint ring system in the 1990s. But it was orbiter Juno that delivered the closest, longest look at the gas giant

Juno found that the Great Red Spot isn’t just wide – it extends 300km below the cloud tops…

 Juno’s data showed the poles each host a central cyclone surrounded by smaller vortices

The spacecraft has also spotted striking aurorae at Jupiter’s poles, revealed how particles ‘surf’ along magnetic field lines to form these bright emissions, and found that aurorae are actually responsible for heating Jupiter’s whole upper atmosphere to

Destination: Jupiter

Taking up Juno’s mantle, two new robotic probes are en route to Jupiter and its mysterious moons

Come 2031, a pair of new robotic explorers will be investigating Jupiter and its moons: ESA’s Jupiter Icy Moons Explorer (Juice, for short) and NASA’s Europa Clipper, both of which are currently winging their way through the Solar System on their way to the giant planet.

Juice is due to arrive at Jupiter in July 2031 and will explore the entire Jovian system before honing in on Jupiter’s three large and likely ocean-bearing moons: Europa, Ganymede and Callisto. The subsurface oceans on these moons may contain the building blocks for life, making them especially exciting in our hunt for habitable worlds other than Earth. Towards the end of its mission, Juice will hop over to Ganymede, making it the first spacecraft ever to orbit a moon in the outer Solar System.

Europa Clipper, expected to arrive in April 2030, will focus more closely on Europa. The spacecraft will orbit Jupiter and whirl round to closely pass Europa nearly 50 times, snatching repeated glimpses of the moon’s environment and assessing whether it could be friendly to life. Together, the two spacecraft will build on the legacy of Juno to hunt for the ingredients of life, advance our understanding of Jupiter and Ganymede’s magnetism, and explore the gravity that squeezes and squashes Jupiter’s moons as they circle the immense planet.

…and that Jupiter’s aurorae (seen here in infrared) superheat the planet’s atmosphere

surprisingly high temperatures. Juno has seen auroral dawn storms springing to life on the dark (night) side of Jupiter – large, spectacularly bright storms that grow even more luminous as they rotate into the planet’s dayside in the early morning.

Secrets beneath the swirls

“Juno was the first spacecraft to fly repeatedly over the polar auroral regions of an outer planet. Its incredible images of the aurorae are amongst the most detailed ever taken away from Earth at any planet,” says Stallard. Juno has also measured how the aurorae fling particles up into Jupiter’s atmosphere, measurements that “are now fundamental to our changing understanding of Jupiter’s aurorae [and have] dramatically changed our view of how Jupiter’s aurorae form”.

Juno also revealed a lot more about the interior of Jupiter. Before the mission, we were debating whether Jupiter has a solid core of ice, rock and metals, or whether it’s basically gas all the way

Europa Clipper (bottom) and Juice (top) are due to arrive at Jupiter in 2030 and 2031 to carry on Juno’s legacy



Juno’s greatest feat? The craft mapped Jupiter’s magnetic chaos deep into its interior

down. Each has implications for Jupiter’s origin. In the former case, rocky debris clumped together into a solid lump that then grabbed gas from its surroundings, while in the latter, Jupiter instead began life as an infant star before collapsing inwards. Juno has found Jupiter’s core to be larger, more diffuse and ‘fuzzier’ than we expected, containing up to 15 per cent of Jupiter’s mass and spanning around half of Jupiter’s radius. This may point to an origin story somewhere between the aforementioned routes: one where a baby Jupiter, forming as a planet, suffered a direct, powerful impact that disrupted its interior.

Killer magnetism

Spacecraft have to be tough to survive Jupiter’s incredibly strong magnetic field

Jupiter’s magnetic field is truly immense. It extends far beyond the planet itself and is the strongest in the Solar System aside from that of the Sun. This field scoops up and accelerates particles to blistering speeds approaching the speed of light, acting as a giant cosmic particle accelerator. These super-hot particles exist in doughnut-like radiation belts wrapping around Jupiter’s middle; they can damage electronics when they collide with spacecraft, and so missions such as Juno are carefully planned to keep their probes protected.

To avoid the worst of the planet’s radiation, Juno orbits on a highly stretched orbit that skims Jupiter’s poles. This orbit dodges the densest parts of the radiation belts, spending as little time

One of the most exciting findings from Juno concerns Jupiter’s magnetism. Juno has dug into Jupiter’s fuzzy core, finding signs of an internal dynamo, and discovered a surprisingly asymmetric magnetic field across the planet’s northern and southern hemispheres. It’s also revealed that Jupiter’s internal magnetic field evolves with time (a phenomenon also seen on Earth, known as ‘secular variation’, and driven by Jupiter’s deep, dominating winds) and spotted crashing waves and vortices at the outer edges of Jupiter’s magnetic field, where this region bumps up against the stream of radiation flooding into space from the Sun.

in them as possible, and loops through a thin, relatively radiation-free gap sitting just inside Jupiter’s radiation belts (similar to one around Earth that hosts most of our satellites). Even so, “it’s one of the most hostile environments a spacecraft has ever flown through,” says Stallard.

The orbiter’s core instruments are also locked within a radiation-safe

Carefully does it: Juno skimmed the poles, dodging Jupiter’s deadly radiation belts

vault made of titanium. Juno’s principal investigator, Scott Bolton of Southwest Research Institute in San Antonio, Texas, calls Juno “basically an armoured tank”. While not robust enough to block radiation entirely, the vault is sufficient to significantly slow radiation damage to the probe’s science instruments, enabling them to live longer.

Nicky Jenner is a science writer and editor specialising in space and environment

“For me, Juno’s greatest achievement was its detailed measurement of Jupiter’s surface magnetic field, something almost impossible with any other spacecraft,” says Stallard. “It flew so close to the planet, it was able to model the magnetic field down into the interior. In doing so, it revealed a wonderfully distorted field structure. This confusing field tells us that Jupiter has something strange going on in the outer layers of its interior, twisting up magnetic field lines in a unique way.”

Zooming in on the moons

It’s not just the planet itself that Juno helped us to understand; its satellites came under scrutiny too. Jupiter’s hottest moon, Io, is thought to be the most volcanically active world in the Solar System, with this activity driven by the tugging and squeezing of

its parent planet as it whirls round in an extremely close orbit. Juno has found signs of still-warm magma lying just below the moon’s surface, spotted molten lava lakes and hotspots, and – in January of this year – witnessed the most extreme volcanic event in the moon’s known history, when a hotspot larger than Austria spat out over six times the energy output of all the world’s power plants. Additionally, rather than Io hosting an ocean of magma, Juno has instead found that the moon’s 400 or so volcanoes are each fed by their own individual cauldron of hot magma – a finding that reshapes what we thought we knew about volcanism on rocky worlds.

From fiery Io to frozen Europa: Juno found that Jupiter’s fourth-largest moon is highly likely to harbour a vast, salty ocean beneath a thick, icy crust, making it a prime target in our hunt for life. With this in mind, Juno has searched for oxygen on this moon – and found it. As charged particles flow past and collide with Europa, they break surface ice into hydrogen and oxygen, throwing the latter into the atmosphere and potentially down into the subsurface ocean.

Ganymede – the largest moon not only of Jupiter, but the entire Solar System – is also thought to have an ocean. During a close fly-by, Juno spotted mineral salts and organic (carbon-containing) compounds – perhaps remnants of ocean brine that once reached the surface. The spacecraft has also imaged the polar regions and rest of Ganymede in detail, spotting scratches and craters, and captured the moon casting a shadow on Jupiter during an eclipse.

Juno completed its prime mission in 2021 and was granted an extension through 2025. It’s currently slated to end in September, but that’s not set in stone. With NASA still reviewing its budget for 2026 and beyond, the spacecraft may yet have more scientific discoveries ahead. Whenever its final day comes, it’s likely to be sent on a self-destructive ‘death plunge’ into Jupiter’s clouds, to avoid any chance of contaminating Jupiter’s moons – which, thanks to this plucky probe, we now know are among the most promising places to search for life in the Solar System.

2transport?

Rocky mantle

Subsurface ocean Ice shell

Pickup ions

Pickup ion

 Another moon revelation: how radiation and energetic particles break Europa’s ice into hydrogen and oxygen

Juno captured the volcanic peaks at Io’s poles, then (inset) a record-breaking eruption in late 2024

The fundamentals of astronomy for beginners

EXPLAINER

Start with a young star circled by debris. Then let gravity take over. Prep time: a few million years

How to make a planet

From stardust to rocky realms and gas giants, here’s what it takes to build a world

To make a planet, first you’ll need a massive, reasonably dense cloud of cold gas and dust. Luckily, later generations of the cosmos have provided just that. These clouds, rich in hydrogen, helium and elements forged in earlier stars, are the raw ingredients for planets. In the case of Earth, this happened about 4.5 billion years ago. So if you’re starting from scratch, you may want to clear your schedule for the next few aeons…

Next, you’ll need something to give that cloud a cosmic nudge. A nearby supernova blast, a passing star or some other gravitational disturbance will do the trick. This triggers the cloud to begin collapsing under its own gravity. As it contracts, most of the mass falls towards the centre, forming a protostar. The rest flattens into a spinning protoplanetary disc. This is where the magic of planet building happens.

As the protostar continues to feed on surrounding material, it grows hotter and denser. Eventually, its core becomes hot enough to ignite nuclear fusion, and – voilà! – a new star is born. But we’re here for planets, not stars, so let’s turn our attention to what’s still swirling in the disc. This material isn’t all the same

 Some assembly required: clumps of ice and dust grow into planetesimals, the building blocks of future planets

temperature. The farther you go from the star, the cooler it gets. At certain distances, you’ll hit what’s called a snow line (or frost line), the point where gases like water, methane and ammonia are cold enough to condense into ice. As these ices start sticking to dust grains, they form larger and larger clumps. These sticky seeds are called planetesimals.

When other worlds fall to Earth

You could find the evidence for planet building right in your own backyard

Although the process of planet formation isn’t completely understood, the best evidence that we’re on the right track can be found not just across the Solar System, but right here on Earth.

An estimated 17 meteorites a day survive their fiery descent through Earth’s atmosphere. Many of these are fragments of ancient planetesimals – the earliest building blocks of planets. Because meteorites often preserve material from the dawn of the Solar System, studying them offers a unique window into how planets form. There are two main types: chondrites and achondrites. Chondrites, which make up around 90 per cent of meteorite falls, are named after

 Every day, space delivers meteorites like this one – ancient clues to how planets form

chondrules: tiny, round droplets of oncemolten rock. These grains carry chemical and structural clues to the materials and

Once your planetesimal reaches a decent size, gravity takes over. Instead of relying on chance collisions, it begins pulling in nearby particles. These growing clumps sometimes merge with others, forming larger, lumpy bodies called protoplanets. As they get big enough, their gravity forces them into more spherical shapes, and you’re well on your way to forming a planet.

At this stage, you’ll begin to see gaps and rings in the disc, carved out by forming planets as they clear paths through the material. Observatories like Hubble and ALMA have actually captured these incredible features in young planetary systems.

What type will you make?

Now, depending on where in the disc your protoplanet is forming, and how much material it can gather, your protoplanet can become one of four types of planetary body in the Solar System:

 Gas giants, such as Jupiter in our own Solar System, can form via core accretion – where a solid core grows large enough to attract and retain a thick envelope of gas – or through disc instability, where parts of the gas-rich disc collapse directly under their own gravity. The latter is faster, but thought to be rarer and limited to very massive, cool discs.

 Terrestrial planets, like our planet Earth, form from rocky material closer to the star, where it’s too warm for ices to survive. Once the core forms and the planet grows, it goes through four stages: differentiation (heavy stuff sinks, light stuff floats); cratering (asteroids and comets leave their mark); flooding (with lava, water, or both); and surface evolution (thanks to volcanism, tectonics and weather).

 Ice giants, such as Uranus and Neptune, are mostly composed of heavier volatile compounds

processes present in the swirling disc that gave rise to planets.

Achondrites, in contrast, come from larger parent bodies, like asteroids or even planets, that underwent differentiation, forming crusts, mantles and cores. These meteorites are made of igneous rock and help us study the later stages of planetary evolution, like volcanic activity and core formation.

Dating methods such as radiometric analysis have shown that many meteorites are over 4.5 billion years old, making them among the oldest solid materials we can touch. So, if you’re lucky enough to find a meteorite, you’re holding a cosmic time capsule in your hands – a fragment from the earliest days of the Solar System.

 Every planet has to start somewhere… (top left to bottom right): asteroid 2015 TC25, a surviving planetesimal; comet 67P, a two-planetesimal merger; Arrokoth, made from around a dozen; and spheroid dwarf planet Ceres

Jamie Middleton is BBC Sky at Night Magazine’s commissioning editor and has been writing about science for 20 years

like water, methane and ammonia, along with rock and gas. They’re not made of ‘ice’ in the frosty drink sense, but of molecules that were solid beyond their snow lines.

 Dwarf planets, such as Ceres, are small planetary bodies that have enough mass to become round, but not enough to clear out other debris in their orbit. Think of them as planets that didn’t quite win the cosmic game of king of the castle.

So, congratulations! You are now the proud owner of a brand-new planet. Of course, planetary science is still full of mysteries, but as best as we can tell, this is the recipe that likely cooked up Earth and its cosmic cousins.

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SEPTEMBER HIGHLIGHTS

Tuesday

16

If you can find the 28%-lit crescent Moon in daylight this morning, with a small scope or binoculars try spotting mag. –1.9 Jupiter 4.3° south of the Moon’s centre. At 11:00 BST (10:00 UT), the Moon will be 55° above the southwest horizon.

21

Sunday Saturn reaches opposition today and is visible from dusk until dawn.

Wednesday

17

The Moon is now sufficiently out of the way to attempt this month’s Deep-Sky Tour: locating challenging objects on the Aries–Pisces border. Turn to page 56 for more information.



Tuesday

2

The Lunar X and V clair-obscur effects can be seen on this evening’s Moon. Your best view will be around 23:41 BST (22:41 UT).

Thursday

4

This morning, Titan’s shadow transits Saturn’s globe, visible in brightening twilight from 05:38 BST (04:38 UT) until Saturn sets at 08:16 BST (07:16 UT).

Saturday 

27

A double shadow transit can be seen on Jupiter this morning. The shadows of moons Io and Europa will appear to pass across the planet’s globe between 05:54 and 06:41 BST (04:54–05:41 UT).

Monday 

22

The Northern Hemisphere’s autumn equinox occurs today.

Monday

8

This evening, Saturn appears 3.3° south of the 98%-lit waning gibbous Moon.

Friday 

19

Early risers can see brilliant mag. –3.8 Venus just 0.8° from mag. +1.0 Regulus (Alpha (α) Leonis), joined by a 6%-lit crescent Moon. The Moon continues closing on Venus, occulting the planet at 12:48–14:07 BST (11:48–13:07 UT).

12

Friday Saturn’s largest moon, Titan, is eclipsed by the planet’s shadow at 04:10 BST (03:10 UT).

At 21:00 BST (20:00 UT), the rising Moon occults the Pleiades.

28 Io’s shadow Europa’s shadow Io Europa

Sunday The moon Titan is occulted by Saturn’s disc at 02:30 BST (01:30 UT).

Sunday 

7

A total lunar eclipse occurs this evening, the Moon rising at sunset, fully immersed in Earth’s shadow (turn to page 46 for details).

20

Callisto’s shadow

Saturday Titan and its shadow are in sync as they transit Saturn’s disc from 05:13 BST (04:13 UT) until Saturn sets around 07:00 BST (06:00 UT).

 Monday

15

As Jupiter is becoming edge-on to Earth, its interactions with the outer Galilean moon, Callisto, are becoming visible. In the early hours this morning, see its shadow cross Jupiter’s disc between 02:30 and 05:13 BST (01:30–04:13 UT).

Monday At 00:26 BST (23:26 UT on 28 September), Io’s shadow and Ganymede cross Jupiter’s disc together, with Io itself joining in at 01:38 BST (00:38 UT). 29

23

 Tuesday Neptune reaches opposition, lying close to Saturn but much fainter.

Thursday

25

Jupiter’s largest moon, Ganymede, is eclipsed by the shadow of Jupiter at 05:08 BST (04:08 UT).

Family stargazing

The lunar eclipse on the evening of 7 September is conveniently timed for youngsters, as the Moon rises fully eclipsed just as the Sun sets. The Moon’s disc will be much darker than normal when eclipsed, which will make spotting it that much harder. This is a great way to encourage engagement, making a competition out of who can spot the Moon first. Totality ends almost as the Moon is fully above the horizon and this will result in an odd-shaped, fully illuminated section of the Moon probably being the first view of the eclipse. www.bbc.co.uk/cbeebies/shows/stargazing

NEED TO KNOW

The terms and symbols used in The Sky Guide

Universal Time (UT) and British Summer Time (BST)

Universal Time (UT) is the standard time used by astronomers around the world. British Summer Time (BST) is one hour ahead of UT

RA (Right ascension) and dec. (declination)

These coordinates are the night sky’s equivalent of longitude and latitude, describing where an object is on the celestial ‘globe’

Family friendly

Objects marked with this icon are perfect for showing to children

Naked eye

Allow 20 minutes for your eyes to become dark-adapted

Photo opp

Use a CCD, planetary camera or standard DSLR

Binoculars

10x50 recommended

Small/ medium scope

Reflector/SCTunder6inches, refractor under 4 inches

Large scope

Reflector/SCT over 6 inches, refractor over 4 inches

GETTING STARTED IN ASTRONOMY

If you’re new to astronomy, you’ll find two essential reads on our website. Visit bit.ly/stargazingtop-tips to learn how to stargaze in 12 easy steps and bit.ly/choose-firsttelescope for advice on choosing your first scope

Titan’s shadow

THE BIG THREE

20:00 BST (19:00 UT)

The top sights to observe or image this month

20:15 BST (19:15 UT) Moon’s altitude 4o

20:30 BST (19:30 UT) Moon’s altitude 6o

20:45 BST (19:45 UT) Moon’s altitude 8o

 On 7 September around sunset, watch the Moon rising just as totality is coming to an end (Moon’s size exaggerated for clarity)

DON’T MISS

Total lunar eclipse as the Moon rises

BEST TIME TO SEE: 7 September 2025, from moonrise around 19:45 BST (18:45 UT)

Remember the total lunar eclipse back in March? Unfortunately, for many observers across the UK, the weather wasn’t good, but if you were lucky enough to see it, you’ll remember that totality occurred just a few minutes before the Moon set: we got to see the initial partial phase of the eclipse, a hint of totality… and then the Moon was gone. Well, the good news is that this month there’s another total lunar eclipse and, in a way, it’s something of a mirror of the March event.

Whereas in March, totality was reached just as the Moon set, the total eclipse due on 7 September will see the Moon rise already in totality. It appears on the eastern horizon at about 19:45 BST (18:45

UT), around the time the Sun is setting. This causes all sorts of viewing issues, because a totally eclipsed Moon is darker than a normal, uneclipsed Moon. How dark is unknown at this point, but it’s likely to be dark enough to make it tricky to see, low down in the evening twilight through a murky layer of atmosphere.

Totality ends just as the Moon clears the horizon, so the experience for this eclipse, clouds willing, will be similar to what you saw in March, but in reverse. Earth’s dark umbral shadow clears the Moon’s disc shortly after moonrise, and the first impression that’s likely to be evident will be an oddly shaped Moon, almost as if someone has taken a slice of regular Moon and placed it in the sky.

identify the Moon early could lead to missing an important part of the eclipse.

If totality is very dark, this can fool you at first. You might spot the part of the Moon that’s coming out of totality, but – being both small and an unfamiliar shape – you might dismiss it. It’s quite possible that it’ll only be obvious as a part of the Moon when it rises higher in the sky, so be prepared for this, as failing to

The Moon will be rising in the Belt of Venus, a name given to the pink-topped grey band that sits just above the opposite horizon to where the Sun sets. As the evening progresses, the pink colour will reduce and the grey band will deepen. This is Earth’s shadow rising as the Sun sets in the opposite direction. As the evening darkens, the portion of the Moon that’s not covered by the umbral shadow will increase, this being the final partial phase of the eclipse.

Longer exposures reveal the subtle colours within the umbra

Lunar occultation of Venus

BEST TIME TO SEE: 19 September, 12:00–14:20 BST (11:00–13:20 UT)

The Moon occults the planet Venus on 19 September. This will be under full daylight, but mag. –3.8 Venus will still be visible. What might be a little harder is the 5%-lit waning crescent Moon that’s doing the occulting. Here, clear, crisp skies are best, as any haze may obscure the Moon. Venus appears 11 arcseconds across at the time of the occultation, with an 88%-lit gibbous phase. It’s the bright limb of the Moon that first encounters the planet, the event starting around 12:48 BST (11:48 UT) as seen from the centre of the UK. Lunar parallax shifts the Moon’s apparent position relative to Venus, so timings will vary by a few minutes depending on your location. The best strategy is to locate Venus well before the event starts, and remain centred on it.

At occultation start, the Moon’s centre will be 27° from the Sun’s centre, close enough to require caution if you’re using binoculars. Here, the best technique is to stand in the shadow of a building, so the Sun is hidden but the sky to the west

Moon 5%-lit waning crescent

Disappearance

12:48 BST (11:48 UT) Altitude 46o

Reappearance

14:07 BST (13:07 UT) Altitude 38o

Lunar night side shown for clarity (not visible in daylight)

Timings are for central UK and will vary with location. Observe at least 20 minutes before stated times for safety. Solar precautions are advised (the Sun will be 27o away)

(right) of it is clear. Venus will reappear at around 14:07 BST (13:07 UT), though this will test your nerve as you won’t be able to see the dark portion of the Moon from which the planet emerges.

If you doubt your ability to find Venus during the day, one method is to first locate the planet in the early morning

Jupiter moon events

BEST TIME TO SEE: As outlined below

There are several excellent Jupiter moon events to watch out for this month. Because we’re nearing a Jovian equinox (next year), Callisto is now geometrically positioned to be involved in visible events again: the outer Galilean moon can be seen reappearing from behind Jupiter’s disc on 7 September at 04:46 BST (03:46 UT). If you have the means to locate Jupiter in daylight, there’s a Ganymede shadow transit visible in the daytime on 14 September at 11:25–14:36 BST (10:25–13:36 UT).

A Callisto shadow transit occurs on 15 September between 02:30 and 05:13 BST (01:30–04:13 UT). Callisto casts a large, dark shadow on Jupiter, something that can only occur when Jupiter is nearing an equinox. Ganymede is eclipsed by Jupiter’s shadow on 25 September at 05:08 BST (04:08 UT) and there’s a double shadow transit involving Io’s and Europa’s shadows on 27 September at 05:54–06:41 BST (04:54–05:41 UT).

Finally, on the night of 28/29 September, Io’s shadow begins to cross Jupiter’s disc at 00:26 BST (23:26 UT), with Ganymede transiting at the same time. Io itself follows onto the disc from 01:38 BST (00:38 UT), while its shadow moves off the disc at 02:39

dawn twilight sky and, using an equatorially mounted scope, stay with it until the occultation occurs. Admittedly, this does require you to have a few hours spare on the morning of 19 September. Alternatively, locate Venus at 11:25 BST (10:25 UT) when it’s due south at an altitude of 50°.

7 September, 04:46 BST (03:46 UT) Callisto occultation reappearance 15 September, from 02:30 BST (01:30 UT) Callisto shadow transit

25 September, 05:08 BST (04:08 UT) Ganymede eclipse disappearance

29 September, from 00:26 BST (23:26 UT) Io, Io shadow and Ganymede transit; Europa occultation reappearance

 There’s lots of action to catch around Jupiter this month

BST (01:39 UT). Ganymede completes its crossing at 03:41 BST (02:41 UT) and, just minutes later, Io exits at 03:54 BST (02:54 UT), just as Europa reappears from behind Jupiter. A busy evening!

Callisto’s shadow

Callisto

THE PLANETS

Saturn PICK OF THE MONTH

Best time to see: 21 September, 01:00 BST (00:00 UT)

Altitude: 35°

Location: Pisces

Direction: South

Features: Rings, subtle atmospheric features, moons

Recommended equipment: 150mm or larger

Saturn reaches opposition this month on 21 September, rising to a peak altitude of 34° as seen from the centre of the UK. The planet is currently within Pisces, shining away, with a slightly off-white hue, at mag. +0.2 during opposition. On 8 September, it can be seen close to a 98%-lit waning gibbous Moon shortly after both objects rise and the sky darkens, at around 21:00 BST (20:00 UT).

If you had a chance to catch a view of Saturn through a telescope last month, you would have seen the rings were narrow but obvious. At the start of August, the planet’s southern pole was tilted towards Earth by 3.4°, so they appeared like a thin elliptical band around the centre of the globe. However, by 1 September, the tilt angle will have reduced to 2.5° and the rings will be noticeably harder

Our celestial neighbourhood in September

to see again. Saturn underwent a ring plane crossing back in March, but at the time it was poorly placed for observation. The next isn’t due until 2038, but between 11 November and 8 December this year, Saturn will appear to wobble to a very narrow tilt angle of just 0.4°. Although not a true ring plane crossing, that is narrow enough to resemble a crossing through smaller scopes.

On 21 September, when Saturn reaches opposition,

The planets in September

the tilt angle will be 1.8°. Such a narrow tilt continues to offer opportunities to see Titan and its shadow cross the planet’s globe.

At the end of September, Saturn remains at mag. +0.2 and, thanks to a slow westward drift, will have wandered across the border of Pisces back into neighbouring Aquarius. Currently, Saturn and Neptune remain close to one another in the sky, lying 2.6° apart on opposition night, with Neptune located northeast of Saturn.

The phase and relative sizes of the planets this month. Each planet is shown with south at the top, to show its orientation through a telescope

Deneb Kaitos

 Mag. +0.2 Saturn drifts west in Pisces this month, reaching opposition on 21 September

 Saturn and Neptune are visited by a 98%-lit waning Moon on 8 September

Moon

Neptune Saturn

Mercury

Best time to see: 1 September, 30 minutes before sunrise

Altitude: 5.5° (low)

Location: Leo

Direction: East-northeast Mercury is a morning planet at the start of the month, rising 70 minutes before sunrise. On 3 September, the mag. –1.6 planet sits 1.6° from Regulus (Alpha (α) Leonis), the pair visible in the dawn twilight from around 05:40 BST (04:40 UT). Mercury is tricky to see after this, moving to superior conjunction on 13 September and thereafter poorly positioned for the rest of the month.

Venus

Best time to see: 19 September, 12:00 BST (11:00 UT)

Altitude: 45°

Location: Leo

Direction: South-southwest Mag. –3.8 Venus is a morning planet 1.4° south of the Beehive Cluster, M44, on 1 September. On this date, it rises 3 hours before the Sun at 03:20 BST (02:20 UT), giving an hour of darkness to catch it close to the cluster.

On 19 September, Venus is occulted by the Moon from 12:48 to 14:07 BST (11:48–13:07 UT); see page 47 for details. If you’re up early that day, Venus rises around 04:15 BST (03:15 UT), with the then 5%-lit Moon 3.5° to the northwest and Regulus just 0.8° away. By the end of the month, Venus rises 2.5 hours before the Sun, but maintains its impressive mag. –3.8 brightness.

Mars

Evening planet but not visible this month.

Jupiter

Best time to see: 30 September, 06:00 BST (05:00 UT)

Altitude: 50°

Location: Gemini

Direction: Southeast Jupiter improves throughout September, reaching a peak altitude of 28° at around 05:00 BST (04:00 UT) in darkness on 1 September, shining at mag. –1.8. It sits 1° from mag. +3.5 Wasat (Delta (δ) Geminorum), the separation reducing until 6 September to just 10.8 arcminutes. On the morning of 16 September, mag. –1.9 Jupiter is joined by a 30%-lit waning crescent Moon. At the end of the month and shining at mag. –2.0, Jupiter reaches a peak altitude of 50° under deep twilight at around 06:00 BST (05:00 UT).

Uranus

Best time to see: 30 September, 04:30 BST (03:30 UT) Altitude: 57°

Location: Taurus

Direction: South

The planet Uranus reaches a peak altitude of 48° under darkness at the start of the month, the mag. +5.8 planet lying 4.5° south of the Pleiades. It achieves a peak altitude of 57° in darkness from 22 September onwards, brightening slightly to mag. +5.6 by 30 September.

Neptune

Best time to see: 23 September, 01:10 BST (00:10 UT)

Altitude: 36°

Location: Pisces

Direction: South Neptune reaches opposition on 23 September, when it can be found relatively near Saturn, shining at mag. +7.8. It’s currently in Pisces and able to reach a peak altitude of 36° under dark-sky conditions.

JUPITER’S MOONS: SEPTEMBER

Using a small scope you can spot Jupiter’s biggest moons. Their positions change dramatically over the month, as shown on the diagram. The line by each date represents 01:00 BST (00:00 UT).

THE NIGHT SKY – SEPTEMBER

Explore the celestial sphere with our Northern Hemisphere all-sky chart

When to use this chart

1

On other dates, stars will be in slightly different positions because of Earth’s orbital motion. Stars that cross the sky will set in the west four minutes earlier each night.

How to use this chart

1. Hold the chart so the direction you’re facing is at the bottom.

2. The lower half of the chart shows the sky ahead of you.

3. The centre of the chart is the point directly over your head.

Sunrise/sunset in September*

Moonrise in September*

Lunar

in September

MOONWATCH September’s top lunar feature to observe

Lubiniezky

Type: Crater

Size: 45km

Longitude/latitude: 23.9° W, 17.9° S

Age: Around 3.9 billion years

Best time to see: Two days after first quarter (2 September and 1 October) or one day after last quarter (16 September) Minimum equipment: 50mm telescope

There are a vast number of craters visible on the Earth-facing side of the Moon and, indeed, on the far side we can’t see. Classic craters have well-defined sharp rims surrounded by ejecta ramparts. Internally, they exhibit complex terraces leading to a flattish floor with a mountain complex in the centre. This month’s Moonwatch target isn’t like that at all.

Lubiniezky is a 45km ring filled with lava from Mare Nubium, a fine example of what’s known as a ghost crater. For an example of the more ‘classic’ kind of crater, look just to the south of Lubiniezky, where the 61km-wide Bullialdus sits. It absolutely fits the description. Fortunately, the position of both craters means that they’re close to either the morning or the evening terminator at around the same time.

Lubiniezky E

This gives a fantastic opportunity to study, compare and contrast both features under oblique lighting conditions.

For its age – in the region of 3.9 billion years old – Lubiniezky is in remarkably good shape (apart from its insides being completely flooded with lava). It has beautifully curving rim walls largely uninterrupted by any serious impacts. There are a couple of minor exceptions, of course. One is in the northern section, where the ring is interrupted by a 2.1km craterlet and a small, similarly sized gap in the south, where the flat floor joins the external lava surface of Mare Nubium. The rim wall rises sharply above the crater’s floor for most of the circumference, those areas away from the ‘gap’ formed by a steep cliff edge, approximately 400 metres high.

Lubiniezky is a 45km ring filled with lava – a fine example of a ‘ghost crater’

 It’s rewarding to compare and contrast ghostly Lubiniezky with nearby ‘classic’ crater Bullialdus

Pi

Lubiniezky A

Lubiniezky’s beautifully flat floor is impressive, but at close inspection through large instruments or highresolution imaging setups, when the terminator is nearby it has a definite mottled appearance. Apart from a smattering of tiny craterlets, there are a number of 2km sunken craterlets, features which themselves have been completely submerged beneath a layer of lava. At times of oblique illumination, the faint outline of these features may be glimpsed – like ghosts within a ghost. There are several other ghost craters in the region, but Lubiniezky is the best-looking of the bunch. Just to the northwest is the 28km plectrum-shaped form of Lubiniezky A, another flooded crater with a much rougher rim. Immediately to the west of Lubiniezky A is 37km Lubiniezky E, another ghost. This one has a better-defined outline than Lubiniezky A, but is still rather rough and more broken than Lubiniezky. Visible at a similar phase time to Lubiniezky is the similarly sized crater Kies. Lying 256km to the south, Kies has a south-pointing extension that makes it resemble a hand mirror. Immediately west of Kies is a famous dome called Kies Pi. Like other domes on the lunar surface, it’s best seen when the terminator is nearby, as the oblique lighting highlights the appearance of the 145m-high and 13km-diameter lunar dome.

Bullialdus MARE

Kies

Lubiniezky

COMETS AND ASTEROIDS

Comet C/2024 E1 arrives from the distant Oort cloud

Comet C/2024 E1 (Wierzchoś) is set to be a slow burner throughout the autumn, rising from a dim 13th magnitude at the start of September to possibly mag. +5 at the start of 2026. Sadly, at its brightest it will be in southern Sagittarius, too low and too close to the Sun to be seen properly from the UK. But that doesn’t mean we can’t enjoy the show until mid-November, by which time the comet will hopefully be approaching eighth magnitude.

This is a hyperbolic comet inbound from the Oort cloud. It was discovered in March 2024 by the Polish astronomer Kacper Wierzchoś during a routine survey at Mount Lemmon Observatory in the Santa Catalina Mountains, Arizona. It was captured by an f/1.6, 1.5-metre Cassegrain telescope using a 111.5MP CCD camera, when it was around 20th magnitude. Its perihelion will be 20 January 2026, when it will swing past the Sun at a distance of 0.5656 AU (84.6 million kilometres).

Two for one: a second comet will join C/2024 E1 in October

On 1 September, at an estimated mag. +13.1, C/2024 E1 will be 10° north of mag. +4.1 Epsilon (ε) Coronae Borealis. It passes just east of it on 22 September, having increased to around mag. +12.5. It continues southward, passing west of mag. +3.7 Gamma (γ) Herculis on the

STAR OF THE MONTH

Caph, a signpost on the celestial sphere

Few constellations are as easy to recognise as the ‘W’ of Cassiopeia. From the UK, this distinctive circumpolar pattern is as familiar as the Plough. The ‘W’ is formed from five medium-brightness stars. Caph (Beta (β) Cassiopeiae) marks the western end, the right-hand edge of the ‘W’.

The star gets its name from ‘al-Kaff al-Khadib’, meaning ‘the stained hand’, as the preIslamic Arabic depiction of the five stars formed an outstretched hand. The phrase was shortened and came to refer to just Beta Cassiopeiae. It’s a Delta Scuti variable star, ranging from mag. +2.25 to mag. +2.31, with a spectral

class of F2 III, indicating it’s a yellow-white giant.

Caph is 54.7 lightyears away. It has a mass nearly twice that of our own Sun and is 3.8 times larger and 21 times more luminous. It rotates at a velocity of 72.4km/s. At this speed, Caph must be distorted into an oblate spheroid with an equatorial radius 24 per cent larger than its polar radius.

If you draw a line from Caph through Alpheratz (Alpha (α) Andromedae) and extend it for the same distance again, the position in the sky you arrive at is the vernal equinox, the point where the Sun’s apparent motion takes it from the southern to northern

evening of 8 October, when it will have brightened to mag. +11.9.

For added interest, slightly brighter comet C/2025 A6 (Lemmon) will be shining around mag. +10 in late October, passing south of Corona Borealis. The two comets end October around 8° apart.

 Caph (Beta (β) Cassiopeiae) lies on the equinoctial colure, a great circle that passes through the north and south celestial poles

celestial hemisphere on the first day of astronomical spring. Together with Algenib (Gamma (γ) Pegasi), the three stars make the ‘Three Guides’ that mark a great circle in the sky known as the equinoctial colure. If you extend the line, eventually it passes through the position of the autumn equinox, which currently lies in Virgo.

Great

BINOCULAR TOUR

With Steve Tonkin

Swing your binos to Aquarius to find clusters and nebulae, plus a bonus asteroid

1. Psi Aquarii group

This colourful grouping of stars spans nearly 5° of sky, from mag. +5.0 Psi3 (ψ3) Aquarii to mag. +5.6 96 Aquarii. The colours range from bluewhite mag. +5.5 Psi2 (ψ2) Aquarii (spectral type B) to orange-red mag. +4.2 Phi (φ) Aquarii (spectral type M), with all the intervening spectral types (AFGK) represented. Can you arrange them in colour order and identify which star is which spectral type?  SEEN IT

2. M2

Our next target, the globular cluster M2, is easy to find due north of mag. +2.9 Sadalsuud (Beta (β) Aquarii) and due west of mag. +2.9 Sadalmelik (Alpha (α) Aquarii). It is obvious in a star-sparse region of sky and you may see it as Charles Messier himself did: “a nebula without stars.” If you use averted vision (direct your gaze away from it), it will appear to grow slightly and may seem very slightly oval.  SEEN IT

3. Hebe

6 Hebe is the fifth-brightest asteroid and is thought to be the source of around 40 per cent of the meteorites that strike Earth. Use the chart to locate it as it moves southwest, shining at mag.+7.7 early in the month. Although it dims by about half a magnitude later in September, this is offset by the departure of the bright Moon. Track it against the many stars near its path.  SEEN IT

4. The Helix Nebula

A transparent sky, a clear southern horizon and full dark adaptation are prerequisites to get a good look at planetary nebula NGC 7293, the largest visible from the UK. Use the chart to identify mag. +5.2 Upsilon (υ) Aquarii. Look slightly more than 1° to the west, where you should see a faint disc about 13 arcminutes in diameter. Once you have identified it, see if averted vision will reveal any slight brightening to the north.  SEEN IT

5. M30

Our second globular cluster is smaller, fainter and lower in the sky than M2. Find mag. +5.2 41 Capricorni and the cluster is 0.5° to the west, looking like a defocused star. If you want to try a ‘Messier marathon’ next spring (observing all the Messier objects between dusk and dawn), M30 is among the most difficult. Late summer evenings are a very good time to practise finding it!  SEEN IT

6. The Saturn Nebula NGC 7009 is a good observing challenge in UK skies, for which you’ll need the same conditions as you did for the Helix. Fortunately, it’s simple to locate, 1.3° due west of mag. +4.5 Nu (ν) Aquarii. It will look like a slightly defocused star; to detect the elongated lobes that confer its similarity to Saturn would call for considerably more magnification, averted vision and a UHC or OIII filter.  SEEN IT

 Tick the box when you’ve seen each one ✓

THE SKY GUIDE CHALLENGE

Find as many of the Solar System’s moons as your optics – and skies – will allow

Our Solar System is home to hundreds of moons, but how many can you observe? Some – like our own and the brighter ones around Jupiter and Saturn – are relatively easy to see with the naked eye, binoculars or a small telescope. Some even claim that Jupiter’s outer Galilean moons, Callisto and Ganymede, can be seen without equipment when at elongation – though this would be a serious challenge, even for those with exceptionally keen eyesight! You can see some, if not all, four Galilean moons using binoculars, provided you can hold them steady. The same goes for Titan, the largest and brightest of Saturn’s moons, though the fainter, amateur-accessible ones require at least a telescope.

Mars has two faint moons, but these can only be glimpsed at a time near opposition and preferably a favourable

Saturn will be one of your happy hunting grounds: this is how its major moons could look on 11 September

one at that. Sadly, you’ll have to wait until February 2027 for the next opposition, and it’s not particularly favourable. Being small, Phobos (diameter 22km) and Deimos (diameter 12km) require a steady night and a large image scale to be caught. You’ll probably need to put those on the back burner for now.

Name PlanetMag. (typical)DifficultyNotes

Luna Earth –12 Easy Naked eye

Phobos Mars +12 Hard Needs a favourable opposition

Deimos Mars +13 Hard Needs a favourable opposition

Io Jupiter+6 Easy Small scope

Europa Jupiter+6 Easy Small scope

GanymedeJupiter+5.5 Easy Small scope

Callisto Jupiter+6.5 Easy Small scope

Mimas Saturn +12.9 Tricky Stays close to Saturn

EnceladusSaturn +11.7

ModerateRemains relatively close to Saturn

Tethys Saturn +10.2 Easy Small scope

Dione Saturn +10.4 Easy Small scope

Rhea Saturn +9.7 Easy Small scope

Titan Saturn +8.3 Easy Small scope

HyperionSaturn +14.2

ModerateDim and swings wide of Saturn

Iapetus Saturn +10.2 to +11.9 Easy Brighter when west of Saturn

Phoebe Saturn +16.5 Hard Large and highly inclined orbit

Miranda Uranus+16.5 Hard Stays close to Uranus

Ariel Uranus+14.4

Umbriel Uranus+15

Titania Uranus+13.9

Oberon Uranus+14.1

ModerateLarge scope or planetary imaging setup

ModerateLarge scope or planetary imaging setup

ModerateLarge scope or planetary imaging setup

ModerateLarge scope or planetary imaging setup

Triton Neptune+13.5 Fairly easyLarge scope or planetary imaging setup

The outer planets, Uranus and Neptune, have a good number of natural satellites, but many are too faint to see with amateur kit. In the case of Uranus, there are five that may be seen, although – as with Mars – you’ll need a good image scale to grab them. You’ll have to set your camera to overexpose the planet in order to catch the moons. Oberon, Titania, Umbriel and Ariel shouldn’t prove too hard for planetary imaging setups, but the inner moon Miranda can prove elusive and take several attempts.

For Neptune, it’s the planet’s largest moon, Triton, that’s within reach. Surprisingly for such a distant world, Triton is relatively easy to capture. Neptune typically shines at around mag. +7.9, while Triton hovers near 13th magnitude. For visual attempts, use a large aperture and high-power eyepiece, ideally on a night of steady seeing. The same goes for imaging: an extended exposure that overexposes the planet should reveal the presence of this 1,700km-diameter moon.

It may take a while to record all of these moons, especially since capturing Phobos and Deimos requires waiting for a favourable opposition of Mars. Keep a log of the ones you’ve observed, and once you’ve covered the more accessible targets, there are still a few fainter and more challenging moons around Jupiter and Saturn to extend your moon-hunting adventure even further.

 The Solar System moons that are within amateur reach – some easier than others. How many can you tick off?

DEEP-SKY TOUR

1 NGC 697

Not to be unkind, but Aries isn’t generally regarded as a rich haven for amateur deep-sky jewels. However, we’re going to look hard and visit a light smattering of objects near the Aries–Pisces border. Our first target is NGC 697, a 13th-magnitude galaxy 1.7° north-northwest of mag. +2.6 Sheratan (Beta (β) Arietis). Alternatively, locate mag. +5.8 1 Arietis and you’ll find NGC 697 0.3° to the east. It can be seen through a 150mm scope, but it’ll be a struggle, right on the edge of visibility. Larger scopes show it as a faint elongated glow 1.5–2.0 arcminutes long and roughly half that size wide.  SEEN IT

2 NGC 691

Think Aries is just dim and dull? These six quietly fascinating objects prove otherwise

We can use 1 Arietis to find our next target, the unbarred spiral galaxy NGC 691. First, take a moment to look at 1 Arietis. It’s a beautiful double, consisting of a deep-yellow mag. +6.4 primary and a mag. +7.2 light-blue secondary, 2.9 arcseconds apart. Head 1.5° south from 1 Arietis to find mag. +11.6 NGC 691, visible with a 150mm scope as a circular patch. A 250mm or larger scope reveals the object to be around 2 arcminutes across and flattened into a wide oval. There’s the vaguest hint of brightening towards the core, but overall, its appearance is fairly smooth. NGC 691 is part of the NGC 691 galaxy group and, along with NGC 697, is 120 million or so lightyears away.  SEEN IT

3 NGC 772

To locate mag. +10.3 galaxy NGC 772, look 2° south of NGC 691 and then 2° east. Alternatively, head 1.4° east-southeast from the double star mag. +3.9 Mesarthim (Gamma (γ) Arietis). NGC 772 is another unbarred spiral galaxy, closer than the previous two, at 106 million lightyears. Physically it’s large, with a diameter of 200,000 lightyears – twice that of our Milky Way. A 150mm scope shows an object that brightens to a star-like nucleus. Larger apertures will show a mottled, granular texture to the core region, a 300mm scope

This Deep-Sky Tour has been automated ASCOM-enabled Go-To mounts can take you to this month’s targets at the touch of a button. Find the Deep-Sky Tour file in our free Bonus Content online.

showing an object 3.5 x 1.5 arcminutes in size. NGC 772 is also known as Arp 78 and the Fiddlehead Galaxy.  SEEN IT

4 M74

 If our third target, NGC 772, looks lopsided, that’s because it’s being distorted by nearby galaxy NGC 770 (seen just below and right)

Let’s now pop across the Pisces border for mag. +9.6 M74. A 150mm scope shows this face-on spiral as a 6-arcminute patch with a defined, bright core, much larger and brighter than our previous targets, thanks to its relatively close 32-millionlightyear distance. However, its orientation reduces its surface brightness, a 250mm scope showing an 8-arcminute circular glow with a granular core. Larger scopes reveal structure in the faint outer spiral arms, like a dinner plate cracked into distinct pieces. It’s easy to locate: extend a line from Hamal (Alpha (α) Arietis) through Sheratan for about twice the distance to find mag. +3.6 Eta (η) Piscium. M74 lies 1.3° and a fraction north of this star.  SEEN IT

5 NGC 877

From M74, head 2° south and 10° east to venture back into dim Aries galaxy territory. NGC 877 is a mag. +11.8 intermediate spiral and the brightest member of the NGC 877 group of galaxies. Located 160 million lightyears from Earth, NGC 877 is around 115,000 lightyears across, making it larger than the Milky Way Galaxy. A 250mm scope shows a faint elliptical patch a little over 1.5 arcminutes in length and about three quarters of an arcminute in width. A 300mm instrument retains the 2:1 dimension ratio but shows a marginally larger object 2 x 1 arcminutes in size. Its shape is generally well defined. Other galaxies in the group are pretty faint.  SEEN IT

6 NGC 821

FREE BONUS CONTENT

Print this chart and take the Go-To tour www.skyatnight magazine.com/ bonus-content

Head 4.4° southwest from NGC 877 to locate the final galaxy in our tour. This is mag. +11.3 NGC 821, lying near the border between Aries, Pisces and Cetus. Unlike our previous targets, it’s an elliptical galaxy, classed as an E6 type (moderately elongated). It has a physical diameter estimated at 55,000 lightyears and is roughly 75.8 million lightyears away. It’s seen as a weak oval glow through a 250mm scope. Appearing with an apparent size of 1.5 x 0.5 arcminutes, its surface brightness is low. Visually, it appears as a bright core surrounded by a weak outer glow. The core is even more apparent through a 300mm scope, brightening to an almost star-like point.  SEEN IT

AT A GLANCE

How the Sky Guide events will appear in September

8 September: 98%-lit waning gibbous Moon near Saturn and Neptune 12 September: 67%-lit waning gibbous Moon occults the Pleiades 16 September: 28%-lit waning crescent Moon near Jupiter (daylight) 19 September: 6%-lit waning crescent Moon near Venus and Regulus

The Moon

Moonwatch Deep-Sky Tour

The Big Three Total lunar eclipse as the Moon rises (page 46) Lunar occultation of Venus (page 47)

moon events (page 47)

Eclipse España

One country, three years, three eclipses

The total solar eclipse in 2026 is Spain’s first in over a century, kicking off a remarkable 18 months of Spanish Moon-shadow fever. Jamie Carter is your tour guide

Sun, sangria and… solar eclipses? Over the next few years, Spain will offer front-row seats to some of the most spectacular celestial shows on Earth, with three ‘central’ – that is, total or annular – solar eclipses in less than 18 months. This astonishing sequence looks set to make it Europe’s eclipse-chasing epicentre for the rest of the decade. The standout is on Wednesday 12 August 2026: Spain’s first total solar eclipse in over a century, during which a short totality will briefly reveal to the naked eye the sun’s corona (Spanish for ‘crown’, incidentally), its tenuous outer atmosphere.

On that date, a path of totality will pass over the Arctic, Greenland, Iceland, the Atlantic, a speck of Portugal and northern Spain. Occurring just before sunset, totality will last under two minutes, first kissing Galicia

The Moon’s shadow sweeps over Spain, the first of three spectacular eclipses to cross the country in 2026, 2027 and 2028

on Spain’s north coast, crossing a 290km-wide (180-mile) swathe to the Costa del Azahar and Costa Dorada before sinking beneath the Mediterranean Sea as seen from the Balearic Islands. If you were to look at Spain from space, the Moon’s shadow would take just six minutes to cross the country, accelerating to over 32,000km/h (20,000mph) as it races toward sunset and slips off the edge of the Earth.

It will be 121 years since this last happened. Although a slice of northwestern Spain briefly experienced a hybrid eclipse – just one second of totality – on 17 April 1912, it was barely noticeable. The 2026 total solar eclipse is unmatched since an almost identical path of totality swept through northern Spain on 30 August 1905.

“It’s the first total solar eclipse visible from Spain in over a century, but in 2027 we will have another total solar eclipse in the southern part of Spain, and an annular in January 2028,” says Eduard Masana Fresno, an astronomer at the Institute of Cosmos Sciences in Barcelona. “Everything we will prepare for next year’s eclipse – logistics, outreach and education – is not for just one eclipse, but three!”

Spain’s first great eclipse

The excitement around the 2026 eclipse is already mounting, with key cities such as Bilbao, Santander, Valladolid, Burgos, Zaragoza and Valencia all set to experience totality. Madrid and Barcelona, however, will narrowly miss out, each witnessing a 99.9 per cent partial eclipse (which in eclipse terms still equals zero totality). With about 12 million people living in those two cities, expect a lot of travel into the path of totality on eclipse day.

Spain lies at the sunset end of the path of totality, with the Sun just 11° above the western horizon when the path of the Moon’s central shadow reaches Galicia at 20:26 local time (18:26 UT). It sinks lower as the path travels southeast, ending in a horizon-

 Totality begins near Galicia at around 20:26 local time (18:26 UT) and exits around 20:33 (18:33 UT) at sunset over the Balearics

proximity totality at 20:31 (18:31 UT). In Majorca, that’s just 10 minutes before sunset.

Dramatic views of the eclipsed Sun hovering low on the horizon are assured, but only for those who have checked out sightlines in advance. “The western horizon must be completely clear, especially in the eastern part of the path,” says Fresno, cautioning against locations with any natural or human-made obstructions. “We’re talking just 4° or even less, so it’s very important.” Spain is the second-most

The eclipsed Sun will hang low in the west before sunset – a clear horizon is a must

Eclipse by day — shooting stars by night

Once 2026’s totality is over, catch one of the best meteor showers of the year

It’s always wise to observe a total solar eclipse away from artificial light. While urban light pollution won’t spoil the view, a sudden security light triggered by the darkness could break the spell at just the wrong moment. However, on 12 August 2026, there’s another reason to escape the cities: the total solar eclipse happens just a few hours before the peak of the Perseid meteor shower.

Totality will briefly darken northern Spain before sunset on the peak night – though you’re unlikely to spot any meteors during the eclipse itself (totality is more like twilight, not true astronomical darkness). But if you’re in a dark-sky location a few hours after the eclipse, you may see dozens of Perseids streaking across the night. Since it’s August

and a new Moon (the necessary condition of a solar eclipse), you’ll also have a good chance of seeing the bright core of the Milky Way rising in the south, higher than it appears from the UK.

It’s also wise logistically to stay near the path of totality after the eclipse. “The eclipse occurs during peak holiday season, and although Spain has an extensive road network, major traffic congestion is expected immediately after the eclipse,” says Fresno. “Avoid travelling until the following day – especially to Madrid or Barcelona – and plan to stay overnight in the eclipse zone to enjoy the region’s beautiful dark skies.” You could even arrive for the 5 August last quarter Moon and enjoy a 10-night stretch of dark, moonless skies before and after the eclipse.

 The flat terrain of Palencia, directly in the path of totality, will offer an unobstructed view

mountainous country in Europe after Switzerland, with the Meseta plateau north of Madrid, the Cantabrian Mountains near the north coast and the mountains near León all potential obstacles.

“The eclipse will be very low in the sky,” says eclipse cartographer Michael Zeiler of www.eclipse-maps. com. “Local terrain, trees and buildings will require careful site selection, as well as backup locations in case of local clouds. Eclipse shadow maps will be an invaluable guide.” At the time of writing, these are soon to be available from the Spanish National Geographic Institute.

There are ways to avoid the need for meticulous planning when choosing your observing location. For example, the region near Palencia and Burgos is relatively flat, the eclipse will occur fairly high above the horizon, and there’s a good chance of clear skies – all of which make it a naturally favourable spot.

With the Moon out of the way, the Perseids could dazzle, peaking just hours after the eclipse

Alternatively, book a tour where observation sites are carefully chosen in advance by astronomers. Either way, eclipse chasers need to think about the chance of clouds blocking the view. “The topography means the south side of the eclipse track is sunnier than the north side,” says eclipse meteorologist Jay Anderson of www.eclipsophile.com. “Stay away from the eastern side of dark mountains. The biggest problem is likely to be thunderstorms, which form on the mountains north of Madrid, but they’ll be in the weather forecasts. It’s a late-in-the-day eclipse, so there’ll be lots of time to move.” Having a car to chase clear skies may be useful.

2027: A second bite

Less than a year later, another extraordinary total solar eclipse will grace Spain. On Monday 2 August 2027, a path of totality will cross the country’s southern regions, including Andalucía. This eclipse belongs to a family of repeating Moon shadows known as Saros 136, famed for producing exceptionally long totalities. In fact, the 2027 eclipse will feature the longest duration of totality remaining this century – albeit much farther southeast, in Egypt. Although many will travel to Luxor for that six minutes and 20 seconds of totality, Tarifa at the tip of Andalucía will see four minutes and 39 seconds – still remarkably long. The ancient Roman ruins of Baelo Claudia nearby will experience just a few seconds less, as will Algeciras and Gibraltar (although avoid the Rock of Gibraltar mountain, which famously generates its own ‘Levanter’ cloud).

Further north, Cádiz, one of Europe’s oldest continuously inhabited cities, will see two minutes

and 47 seconds of totality, while Marbella and Málaga will get three minutes and 11 seconds, and one minute and 51 seconds, respectively.

It won’t boast the record-setting duration of over six minutes seen in Egypt, but Spain’s accessibility, superb infrastructure and favourable climate are sure to make this Andalucían eclipse a popular event. Remarkably, it’s followed 177 days later by something almost as alluring: a ‘ring of fire’.

2028: the Andalucían annular

Completing a remarkable celestial hat-trick, Spain will witness an annular solar eclipse – known as a ring of fire – on 26 January 2028. Unlike a total eclipse, the Moon will be too far from Earth to completely cover the Sun, resulting in a spectacular bright ring around its silhouette. This means the entire event must be viewed through eclipse glasses.

Geographically, the path of annularity is a mash-up of the previous two. Another sunset eclipse, visible from a path that travels southwest to northeast, will appear just 8° above the horizon for a whopping seven minutes and 10 seconds, as seen from Playa de Castilla in Andalucía. Seville, on the centreline of the path, is where eclipse chasers will likely gather, ready to drive into clear skies (January isn’t the kindest month, clouds-wise). Also on the centreline are Cordoba and Valencia, with other locations in the path including Gibraltar, Cádiz, Marbella and Málaga, as well as Faro on Portugal’s south coast. Ibiza in the Balearic Islands will again witness a breathtaking

On the totality trail

Jamie picks his hotspots for a glorious view of 2026’s eclipse

1. Picos de Europa, Cantabrian Mountains

Totality: 1 minute 43 seconds, 9˚ above western horizon

Observe the eclipse from Pico de la Tabla, framed by the rugged peaks of Picos de Europa. Explore! will lead the tour group. www.explore.co.uk

2. A Coruña, Galicia

Totality: 1 minute 15 seconds, 12˚

The Tower of Hercules, a Roman-era lighthouse on the northwest coast, is where to see the eclipse from Galicia’s second city. www.turismo.ga

3. Sigüenza, Guadalajara

Totality: 1 minute 38 seconds, 7˚ AstroTrails sets up at Sigüenza Castle, overlooking cathedrals, cobbled squares and centuries-old charm in a city declared a Historic-Artistic site in 1965. www.astro-trails.com

4. Parque Natural Cañón del Río Lobos, Castile and León

Totality: 1 minute, 42 seconds, 7.5˚

This spectacular 16-mile-long limestone gorge and plateau is one of Spain’s most beautiful landscapes. www.xn--caondelriolobos-zqb.com

 The Roman ruins of Baelo Claudia will see more than four minutes of totality in 2027

5. Observatorio Astrofísico de Javalambre, Teruel

Totality: 1 minute, 27 seconds, 5˚

Perched in the dark skies of the Sierra de Javalambre, home to widefield sky surveys, this is where the European Space Agency is likely to broadcast the eclipse from. www.oajweb.cefca.es

6. Ebro Delta Natural Park, Catalonia

Totality: 1 minute, 31 seconds, 4.4˚

This wetland nature reserve on the Mediterranean Sea is one of the few regions on Spain’s east coast with good sightlines to the eclipse. www.deltadelebreecoturisme.com

7. Majorca, Balearic Islands

Totality: 1 minute 36 seconds, 2.5˚

View the eclipse from Majorca Cathedral in Palma, hike to Mirador de la Trapa or take a catamaran into the Bay of Palma for a sunset view. www.illesbalears.travel

MORE INFO

National Eclipse Commission

www.iaa.csic.es/page/comisionnacional-eclipse

National Astronomical Observatory www.eclipses.ign.es Eclipse262728 www.eclipse262728.es

Climb high into the pristine Picos de Europa for a special spot to witness totality

Total eclipse path 12 August 2026

Annular eclipse path 26 January 2028

Total eclipse path 2 August 2027

 An annular ‘ring of fire’ eclipse will sweep a large portion of Spain from southwest to northeast on 26 January 2028, again at sunset

Jamie Carter is a seasoned eclipse chaser and editor of www.whenisthe nexteclipse.com

eclipse just before sunset, with Majorca seeing a brilliant ring sink into the Mediterranean.

Chasing totality? Plan ahead

Three central solar eclipses all occurring in the same small country within 18 months is phenomenal. That two of them will be at sunset while another features a totality of over four minutes is almost unbelievable. However, there’s something about the 2026 total solar eclipse that makes it an extra-special opportunity.

“Except for the Mediterranean coast and the Balearic Islands, the path of totality crosses some of the most unpopulated areas of Spain,” says Fresno, adding that the path of totality contains everything

 This shows the paths of totality for the total solar eclipses of 12 August 2026 and 2 August 2027, as well as the path of annularity for the ‘ring of fire’ eclipse on 26 January 2028, offering millions of people the chance to witness one of nature’s most awe-inspiring spectacles

 With panoramic views west, Capilla de la Atalaya on the north coast will be an ideal lookout when the 2026 eclipse action begins

from castles, cathedrals and mountains to plazas, local cuisine and wineries. “Take advantage of this opportunity to visit areas you have never seen before. Spain is much more than bulls, flamenco and sangria – so plan ahead.”

Exploring the world is a big part of what eclipse chasing is all about, but so are logistics. With Spain’s 2026 total solar eclipse falling during the summer holidays, and accommodation within the path scarce (not to mention sightlines to think about), it’s time to plan, plan, plan. Only then can you be confident of experiencing mainland Europe’s first total solar eclipse since 11 August 1999 and spending precious moments under the shadow of the Moon.

Misprint, duplicate, or something else? This lenticular galaxy may – or may not – be the missing object M102

Messier 102 The mystery of

Deep within the popular Messier Catalogue of deep-sky objects lies an enigma. Mark Hardaker investigates the curious case of M102

The Messier Catalogue is one of the most well-known collections of astronomical objects. Compiled in the 18th century by French astronomer and avid comet hunter Charles Messier as a quick reference of non-cometary bodies he could ignore, today it serves as a comprehensive list of some of the deep sky’s most alluring objects to observe.

Among its entries are various nebulae, star clusters and galaxies, but one entry in particular, Messier 102 (or M102), has sparked considerable controversy and debate within the astronomical community.

M102 was originally recorded by Messier’s assistant Pierre Méchain in spring 1781. Méchain made many of the discoveries in the catalogue, which Messier usually confirmed before recording. However, under pressure to publish in the annual French almanac Connaissance des Temps, Messier entered M102 without a position, though he later pencilled one in his personal copy.

 Pierre Méchain claimed M102 was a duplicate of M101 – but that didn’t settle the debate

This ambiguity has prompted a long-standing debate: is M102 simply an erroneous duplicate of M101, or is it another celestial body entirely that has yet to be accurately identified? Compounding the issue is the fact that M101 and M102 are not in any way similar.

The entry for M101 reads: “101. Nebula without stars, very obscure and pretty large, between 6 and 7 arcmins in diameter, between the left hand of Boötes and the tail of Ursa Major. Difficult to distinguish when graticule lit.”

Thanks to the expansion of our cosmic view since the 1780s, we now know M101 is a galaxy, not a nebula. M102 may be one too – that, and much else about it, remains unclear…

Is it actually M101?

The entry for M102 reads: “102. Nebula between the stars Omicron Boötis and Iota Draconis: it is very faint, near it is a star of sixth magnitude.”

But that’s where the certainty ends. In 1783, Méchain wrote to astronomer Johann Bernoulli III in Berlin, claiming that his original observation was incorrect and that he had simply made a duplicate observation of nearby M101. In short, there was no M102.

The strongest argument for M102 being a duplicate of M101 is the retraction from Méchain himself. He clearly thought he’d seen the same ‘nebula’ twice. Given that Messier documented M101 shortly before M102, it’s plausible that the two observations were confused – especially given the limitations of 18th-century telescopes. Remember, Messier was observing from the middle of Paris, using an early achromatic refractor with an aperture of only around 90mm (3.5 inches).

This hypothesis is bolstered by the fact that there are no other known celestial objects in the position given in Messier’s description of M102, casting

additional doubt on its validity as a distinct entity. In his 2014 book, The Messier Objects, American astronomer Stephen O’Meara argues powerfully in favour of this solution to the mystery.

On the other hand, some astronomers propose that M102 refers to a different object entirely – specifically NGC 5866, also known as the Spindle Galaxy. Located in the constellation Draco, NGC 5866 has characteristics that align with Messier’s description. This galaxy exhibits a prominent dust lane and a unique edge-on profile that makes it visually distinct from the larger, face-on M101 (also known as the Pinwheel Galaxy).

What’s more, Messier’s description of M102 as being “…between the stars Omicron Boötis and Iota Draconis” is clearly wrong, as those two stars are over 40° apart in the sky. In 1844, British Admiral William Smyth suggested that Theta Boötis may have been misprinted as Omicron Boötis on Messier’s star

 If NGC 5866 is M102, it’s hard to imagine how it was ever mistaken for M101. Here they are side by side: M101, the

charts. NGC 5866 is indeed halfway between Theta Boötis and Iota Draconis, which are only 11° apart.

And does NGC 5866 tally with Messier’s continued description: “… it is very faint, near it is a star of sixth magnitude”? As it turns out, yes: there is a sixthmagnitude star, HIP 73909, lying nearby and nearly due south. The SEDS Messier Catalogue website supports the idea that M102 is indeed NGC 5866.

The plot thickens

But there are further candidates for M102 besides NGC 5866. These include nearby NGC 5907, the well-known edge-on Splinter Galaxy, as well as NGC 5905 and NGC 5879, both members of the same NGC 5866 Group of galaxies in Draco. However, all of these objects are fainter than NGC 5866 and would have been considerably more difficult to see with Messier’s basic equipment.

The ongoing debate surrounding M102 highlights a broader challenge in historical astronomy. The lack of precise observational data from the 18th century makes it difficult to determine the true identities of many catalogued celestial objects.

While several British astronomers lean towards the view that M102 is simply a duplicate observation of M101, others – particularly in the USA – advocate for a more nuanced approach that considers NGC 5866 or even other unidentified objects as candidates. Indeed, NASA and several smartphone astronomy apps now recognise NGC 5866 as M102.

In the end, the M102 controversy is a reminder of how wonderfully complex astronomy can be. As new technologies and methods evolve, so does our ability to re-evaluate the data of the past. Whether M102 is a duplicate, a unique entity, or a different object entirely may remain unsolved, but the ongoing search for clarity is a testament to the enduring intrigue of our Universe.

 For more about how humans have catalogued the night sky, read our feature over the page

Mark Hardaker is an amateur astronomer, writer and communicator

Pinwheel Galaxy (left) and (at the same image scale) NGC 5866, the Spindle Galaxy (right). You be the judge

 Prime suspect: NGC 5866 is the galaxy most often identified as the disputed M102 in Messier’s Catalogue

Why do Orion’s stars wear many labels? We explore the catalogues behind the cosmos

ORION

 Astronomers have long sought to create systems for organising the night sky

heavens Charting the

For centuries, astronomical catalogues have helped bring order to the boundless cosmos. Pete Lawrence takes a deep dive into the essential databases every astronomer should know

Star and deep-sky catalogues are crucial resources for making sense of the night sky. There are a lot of them, though – so many, in fact, that you almost need a catalogue of catalogues to keep track of them all!

There’s a rich history wrapped up in the creation of these databases, and many astronomical objects appear in multiple catalogues, each with its own naming convensions and quirks. In this guide, we’ll explore some of the widely used catalogues and the types of celestial objects they cover, from nearby stars to distant galaxies.

With massive amounts of high-precision data now streaming into mainstream planetarium apps, what role do older catalogues play? Stars and deep-sky objects may not change rapidly, but when it comes to pinpoint accuracy, even small shifts can matter. We’ll look at which catalogues are being actively maintained and refined.

If you’ve ever wondered what those odd suffixed numbers on star maps mean, read on and be impressed by how human beings have brought structure to the cosmos.

Star catalogues we all start with

We’ll begin with the star catalogues that any new or experienced astronomer is likely to encounter.

The Bayer star labelling system was compiled by German astronomer Johann Bayer and published in 1603 as part of his Uranometria star atlas. Bright constellation stars were given a Greek letter in order of descending brightness. When all 24 Greek alphabet characters were exhausted, Roman letters a–z were used, then A–Q. Beyond Q, we find the beginnings of the variable star labelling system, variables identified with R–Z then RR, RS, RT, and so on, to ZZ. Similar brightness levels and long-term variability mean that some Bayer labels appear out of sequence.

For example, Betelgeuse (Alpha (α) Orionis) is currently dimmer than Rigel (Beta (β) Orionis).

English astronomer John Flamsteed published his Historia Coelestis Britannica in 1725, using numbers instead of letters to catalogue 2,554 stars grouped by constellation. Each group starts at 1 and increments with increasing right ascension; numbers get higher west to east. Like the Bayer catalogue, values are followed by the genitive form of the constellation name. For example, 12 Cassiopeiae, 14 Geminorum, and so on. Interestingly, 34 Tauri was actually the earliest known sighting of Uranus, recorded 91 years earlier than its formal discovery by William Herschel in 1781.

Photometry Catalogue published in 1908. The first version of the YBSC was published in 1930.

The Yale Bright Star Catalogue (YBSC) lists 9,110 entries brighter than mag. +6.5. Most catalogues have anomalies, and the YBSC is no exception, 11 entries being bright novae/supernovae when catalogued and four are deep-sky objects. The information on its 9,095 genuine stars is actively updated. Identifiers are prefixed with BS, YBS or sometimes HR, a reference to the Harvard Revised

Keeping track of your epoch

 Sirius appears as HR 2491 in the Yale Bright Star Catalogue, HIP 32349 in the Hipparcos Catalogue and TYC 5949-2777-1 in both Tycho-1 and Tycho-2

As Earth and the stars are constantly moving, it matters when your star catalogue was created

A common issue with older catalogues was that of epoch. You may have noticed that some star data is followed by a date, such as (1950.0) or (2000.0). This is the epoch of that data. Catalogue right ascension (RA) and declination (dec.) values will only be correct for the stated epoch. Proper motion and the shift of Earth’s orbit moves objects by a tiny amount over time, which leads to increasing positional errors within printed catalogues as you move away from the epoch time.

Before the modern computer age, to calculate a star’s precise current position you’d use a catalogue to get its

RA and dec. for a set epoch. You would then use the star’s proper motion to calculate its current position offset from the catalogue’s epoch.

Computers can now do this calculation on the fly, allowing you to see an object’s precise position with up-to-theminute accuracy. Amazingly, it’s now possible to hold entire catalogues in your hand – even a basic smartphone has enough computing power to display the corrected positions for your current date and time. Although we can’t perceive it, the cosmos is in constant relative motion; epochs allow us to account for this and preserve highprecision astrometric data.

The Tycho-2 Catalogue (2000) contains information on 2,539,913 of the brightest stars. It records position, proper motion and photometric data of stars, including doubles separated by more than 0.8 arcseconds down to approximately magnitude +11.5. Identifiers are prefixed by TYC, because the catalogue is a refinement of the Tycho-1 Catalogue (which was created in 1997, consisting of 1 million entries down to mag. +11.0) using data from ESA’s Hipparcos mission and improved data reduction.

The Hipparcos Catalogue published in 1997 contains high-precision astrometric and photometric data, including particularly accurate parallax measurements, on 118,218 stars. Its entries are prefixed with HIP.

Another common star prefix is HD, which refers to the Henry Draper Catalogue published in 1918–24. It’s a large catalogue of 225,300 entries and is notable because it contains details pertaining to stellar spectra. An extension was made in 1949,

How Barnard’s Star is moving relative to the star field, rendering older references out of date

TYC 3828-0019-1

GSC 3827-0420

TYC 3827-0457-1

TYC 3825-0019-1

TYC 3825-0024-1

TYC 3825-0027-1

TYC 3825-0044-1

M97

TYC 3824-1052-1

TYC 3827-0332-1

TYC 3827-0366-1

TYC 3827-0399-1

HIP 54709

TYC 3824-1064-1

HIP 54765

TYC 3824-1040-1

TYC 3824-1055-1

TYC 3824-0995-1

component (single or part of a multiple system) sequence within that region region of sky

taking the total entries to 359,083. The prefix HDE is sometimes used for extension entries, but more often than not, they are simply prefixed with HD.

Big-data star catalogues

Here are some other significant and intriguing astronomical catalogues that you may come across: USNO-B1.0 is a massive all-sky star catalogue listing 1,042,618,261 objects down to mag. +21, providing astronomers with highly accurate positions, proper motions and magnitudes in various optical light filters. The even more comprehensive NOMAD (Naval Observatory Merged Astrometric Dataset) contains over a billion entries merged from Hipparcos, Tycho-2, UCAC2 and USNO-B1.0.

Hercules

 Messier 97’s stellar neighbourhood, showing Hipparcos, GSC and Tycho identifiers, and how Tycho’s three-part naming system works

The UCAC2 (USNO CCD Astrograph Catalog), meanwhile, covers over 48 million stars between declination –90 to +40 with an R magnitude between +7.5 and +16. There is also the SAO Catalogue (Smithsonian Astrophysical Observatory), an older but still significant astrometric database of 258,997 stars, with its identifiers prefixed with SAO.

The Struve Double Star Catalogue, compiled by pioneering astronomers Friedrich von Struve and, subsequently, his son Otto, is dedicated to visual double stars. Friedrich’s entries are prefixed Σ and Otto’s with ΟΣ. A later appendix uses the prefix ΟΣΣ

There is also the more actively maintained Washington Double Star Catalogue (WDS) which has details pertaining to 157,155 double stars. Started in 1964 as the successor to the Index Catalogue of Visual Double Stars, it contains details on 37,404 physical and 8,582 optical doubles, with 111,169 currently in an unknown state.

 The Moon approaching the Pleiades, each star tagged with its Flamsteed number and ZC identifier

The GSC (Guide Star Catalogue or Hubble Space Telescope Guide Star Catalogue) second revision – GSC-II – was specifically compiled to support the precise pointing and navigation of the Hubble Space Telescope. It contains over 945 million entries.

Also notable is the Zodiacal Catalogue (ZC) published in 1940, which includes 3,539 stars brighter than mag. +8.5 within 8° of the ecliptic which may be occulted by the Moon. Identifiers are prefixed ZC.

Deep-sky objects

There are an equally large number of catalogues of deep-sky objects. Many are for specialist astronomy, but here are the common ones that amateurs use.

Messier Catalogue entries are identified using M followed by a number. For many, this is one of the first catalogues that they’ll encounter, listing 110 showcase deep-sky objects. Charles Messier was a comet hunter and compiled the catalogue

and

Galaxy

are among the best-known Messier objects, but

NGC catalogue and others, reflecting how deep-sky objects have been classified by type and historical context

 Left to right: the Crab Nebula (M1),

Cluster (M13)

Whirlpool

(M51)

also appear in Dreyer’s

ANDROMEDA

Alpheratz

between 1774 and 1781 to be a list of things not to confuse for comets. Originally, it only contained 103 entries, the remaining seven added at a later date by other astronomers reviewing Messier’s notes. There are several anomalies within Messier’s Catalogue, such as M40, which is an optical double star and M73, which is an asterism in Aquarius. Its most southerly object is M7, Ptolemy’s Cluster, at declination –34.8°.

Classics and curiosities

The NGC (New General Catalogue) is very familiar to those who like to observe deep-sky objects. It contains 7,840 of them and was originally compiled by John Dreyer in the 1880s. The IC (Index Catalogue) was the first major update to the NGC, adding a further 5,386 objects. Both it and the NGC have errors and spurious entries, many of which have been checked and corrected over time. The NGC/IC Project, an undertaking by professional and amateur astronomers to correct errors in the original NGC/IC data, was completed in 2017.

The Sharpless Catalogue (Sh) lists 312 emission nebulae located north of declination –27°. Published by Stewart Sharpless, its identifier prefix is usually

The future is already here

 NGC 1 and NGC 2 in Pegasus, the start of Dreyer’s monumental New General Catalogue

Now you can carry the astrometric power of a space observatory in your pocket, with data on billions of stars going right to your smartphone

The Gaia (Global Astrometric Interferometer for Astrophysics) space observatory, launched by ESA in 2013 and deactivated in March 2025, was dedicated to recording star positions, distances and proper motions in unprecedented detail. It measured more than 1 billion stars down to magnitude +20, with positional accuracy as fine as 24 micro­arcseconds for the brightest stars – that’s equivalent to measuring the thickness of a human hair 1,000km (621 miles) away.

Gaia’s data is being released in phases. Gaia DR1 (Data Release 1) appeared on 14

PEGASUS

NGC 1

NGC 2 NGC 16

69

Sh2, which references the second and final edition of the catalogue published in 1959.

The ARP Catalogue gathers peculiar galaxies. Compiled by Halton Arp in 1966, it’s often referred to as the Atlas of Peculiar Galaxies, and contains 338 entries, unusually sorted by appearance. Numbers 1–101 are individual peculiar spiral galaxies or ones with small companions; 102–145 are ellipticals;

Gaia data is now being integrated into planetarium apps like Stellarium

September 2016 and contained the positions and magnitudes for approximately 1.1 billion stars, as well as the positions and parallaxes for more than two million stars. Released on 25 April 2018, Gaia DR2 provided enhanced information for 1.3 billion stars and added 14,000 Solar System objects. The third release appeared as Gaia EDR3 (Early Data Release 3) on 3 December 2020, before the full release on 13 June 2022.

Each release improves on the previous one. Gaia DR4, expected in late 2026, is projected to have a precision 1.7 times greater than DR2, with

a 4.5 times improvement in proper motion values. The final release will be Gaia DR5, due in 2030, which will have 1.4 times more precision than DR4 and a further 2.8 times improvement in proper motion values.

Amazingly, the early releases are already filtering down into commonly used planetarium apps, such as Stellarium and SkySafari. It’s now possible to walk around with high­precision Gaia data on your smartphone!

The brilliant Hyades cluster has many names: Melotte 25, Collinder 50, Caldwell 41 and Trumpler 10, among others

146–268 individual or groups with neither elliptical nor spiral shapes; 269–327 are double galaxies; and 332–338 lists entries that don’t fit into any of the aforementioned descriptions.

From clusters to challenges

The Abell Catalogue of Planetary Nebulae, compiled in 1966 by George Abell, lists 86 objects believed at the time to be planetary nebulae – although later research revealed that a few, including Abell 11, 32, 76, and 85, are actually something else entirely. The Abell Catalogue of Rich Galaxy Clusters contains details about 4,073

Pete Lawrence is an expert astroimager and a presenter on The Sky at Night

rich galaxy clusters. Many of these, as well as Abell’s planetary nebulae, are regarded as challenge objects for amateurs with large-aperture telescopes.

The Mellotte Catalogue, published in 1915 by British astronomer Philibert Melotte, contains 245 entries prefixed with Mel. It contains 161 open clusters, 81 globulars, two asterisms and one galaxy. Also cluster-centric, the Collinder Catalogue contains 452 open clusters, 11 globulars, six asterisms, one stellar moving group and one stellar association, giving a total of 471 entries, with its identifiers prefixed with Cr. The Trumpler Catalogue of open clusters was published by Robert Trumpler in 1930 and contains 100 entries, 37 of which were unknown before Trumpler began studying them.

Other objects have their own specialist catalogues too. A few more common examples include the UGC (Uppsala General Catalogue) first published in 1973, which contains details on 12,921 galaxies visible from the Northern Hemisphere, and the PGC (Principal Galaxies Catalogue) first published in 1989, describing 73,197 galaxies. The PK Catalogue was compiled by two Czech astronomers, Luboš Perek and Luboš Kohoutek. First published in 1967, then updated in 2000, it lists details of 1,510 planetary nebulae, with its identifiers prefixed with PK.

Finally, the Caldwell Catalogue, identified by the prefix C, is a declination-ordered list of deep-sky objects compiled by The Sky at Night’s own Patrick Moore (Caldwell is one of his middle names). It contains 109 entries, including several bright objects omitted by Messier. The lowest object is C109 at declination –80.8°. It remains a popular alternative to the Messier Catalogue for those who like to hunt deep-sky objects.

Patrick Moore’s Caldwell objects – popular among amateurs – plugged the gaps in Messier’s list

Practical astronomy know-how for every level of expertise

SKILLS FOR STARGAZERS

How to guide your gear with PHD2

Guiding can make or break your long exposures. Here’s how to master it

 For dim, delicate objects like the Crescent Nebula, a guide scope, guide camera and PHD2 keep you locked on – so you can capture all that lovely fine detail

Guiding is essential for deep-sky astrophotography, because even the most precise setups can introduce small tracking errors that affect your images. These are caused by a mix of mechanical flaws, imperfect polar alignment and atmospheric effects, all of which can cause stars to drift during long exposures, resulting in elongation or blur.

By using guiding accessories and specialist guiding software, such as the free PHD2, you can continuously monitor a reference ‘guide’ star and send corrective commands to your mount. This will keep your stars pinpoint-sharp, allowing much longer exposures. Longer exposures mean dramatically improving sharpness and depth, revealing faint details in nebulae, galaxies and star clusters.

Guiding involves mounting a small, secondary telescope (called a guide scope) and a sensitive camera (guide camera) alongside your main imaging telescope and camera. The guide camera takes rapid, repeated exposures of a star in its field of view. PHD2 then analyses the star’s position in each frame. If the star drifts due to tracking errors, PHD2 calculates the necessary correction and instructs the mount to adjust its position, keeping the guide star locked in place. This process runs throughout your imaging session and compensates for both periodic and random tracking errors.

Although PHD2 is designed to be user-friendly, guiding can seem daunting at first because it involves

extra hardware – a guide scope and camera, securely attached and focused – and a software-driven setup, which requires you to enter technical details like focal length and pixel size. You’ll also need to calibrate the system, pick a suitable guide star and get familiar with guiding graphs and RMS error values. However, it all gets much easier with a little practice.

It’s important to start with good polar alignment and a well-balanced mount, as this helps minimise the number of corrections needed. Your guide scope and camera should be precisely focused and able to detect several stars in the field of view – ideally, at least three – for reliable tracking. Clear skies and stable atmospheric conditions are also crucial, as poor atmospheric seeing can make guiding more difficult. A solid, vibration-free setup is essential to prevent unwanted movement and ensure your guiding corrections are accurate. If your camera loses sight of the guide star, PHD2 will flash and beep to alert you, so you can quickly address the issue.

PHD2 gives real-time feedback using guiding graphs and RMS error values. Flat, steady lines in the graph indicate stable guiding, while large swings suggest issues with your setup or weather conditions. RMS Error shows the average guiding correction: lower values (under about 1 arcsecond) mean sharper stars and better images. The guide star should also appear round and unsaturated for accurate results.

With careful setup and a systematic approach, guiding with PHD2 quickly becomes second nature, unlocking the full potential of your equipment. Follow our steps and you’ll soon be capturing sharp, detailed long-exposure images.

What you’ll need

 Laptop or desktop PC running PHD2 guiding software. Download it for free from www.openphdguiding.org

 Sturdy equatorial mount

 Main imaging telescope

 Dedicated guide scope, securely mounted on the main telescope

 Mounting plates/dovetails

 Sensitive guide camera for detecting faint stars

 Power and data cables

 Up-to-date device drivers

Jim Owen is a UK astrophotographer with a passion for capturing galaxies and nebulae

Step by step

Step 1

Download the latest version of PHD2 onto your laptop or observatory computer. Before heading outside, make sure you have all the necessary drivers for your guide camera and mount installed and up to date, as this will help avoid connection issues.

Step 3

Open PHD2. Use the Profile Wizard to configure your setup. Select your guide camera and mount from the options. Enter your guide scope’s focal length and your camera’s pixel size. This helps PHD2 calculate the guiding parameters for your system.

Step 5

Begin looping short exposures (try 1–2 seconds) with your guide camera. Adjust the focus until the stars appear sharp and round. Select a bright star as your guide star, either by clicking on it or letting PHD2 automatically choose the best candidate.

Step 2

Set up your equatorial mount and main telescope; ensure an accurate polar alignment (we used SharpCap). Attach your guide scope and camera to your main rig. Connect all devices to your computer with reliable cables and ensure everything’s secure.

Step 4

Select your equipment profile and connect to both your guide camera and mount. Confirm a successful connection before moving on. If you run into problems, consult PHD2’s help resources or double-check your cables and driver installations.

Step 6

With your mount tracking, click the ‘Guide’ button in PHD2. The software will calibrate by moving the mount in both axes to learn how it responds to corrections. Once calibration is complete, guiding begins. Keep an eye on the guiding graph and RMS Error.

Take the perfect astrophoto with our step-by-step guide

ASTROPHOTOGRAPHY

CAPTURE

Shoot a rising lunar eclipse

Use

our expert

tips to capture the drama as the eclipsed Moon climbs above the horizon

As described on page 46, there will be a total lunar eclipse on 7 September that somewhat mirrors the one that occurred last March. Whereas March’s eclipse took place as the Moon was setting, with totality being achieved just before moonset, this one takes place at moonrise, with totality ending around 15 minutes after the Moon pops up above the horizon (as seen from the centre of the UK). Both events could be reasonably described as frustrating, as neither gives a decent view of totality. Still, if skies are clear, this month’s event should provide a good look at the second partial phase after totality ends.

 A lunar eclipse low on the horizon makes a striking image – if the weather is kind and skies are clear

There are many ways to photograph a lunar eclipse and, as you’d expect, some methods work better than others. Using a smartphone is perfectly acceptable, but the Moon’s apparent diameter of around half a degree will result in a small lunar disc. Yes, you can zoom in with your phone, but the best results will come from staying within your phone’s optical zoom range. Beyond that, you’re into digital zooming territory, which is no better than enlarging the image in post-processing using an image editor. The software increases the number of pixels in the image by interpolating between actual recorded data, filling in gaps with synthetic information.

A better bet is to use a dedicated camera fitted with a lens of at least 400mm focal length on a full-frame sensor. This setup will allow you to capture the Moon as a detailed disc with visible surface features. Mounting the camera on a fixed platform – or, even better, a tracking mount – will help you achieve excellent, sharp images. The bright lunar surface that is exposed after totality won’t typically

Pete Lawrence is an expert astro-imager and a presenter on The Sky at Night

require long exposures and so is unlikely to be subject to trailing. However, if you allow the bright surface to over-expose, you should be able to pull out some of the beautiful umbral colours in the darker part of the shadowed regions. For this, you’ll need slightly longer exposures, which is where a tracking mount becomes especially useful.

Another method is to use a planetary camera setup with a wide enough field of view to be able to capture the entire Moon in a single frame. Planetary setups typically use multi-frame imaging, collecting numerous shots of the same target over a short period of time. Software such as AutoStakkert! (freeware) can then analyse, quality-assess, register and stack the frames to generate a final image with a higher signal-to-noise ratio than the individual frames. The trick here is to make sure you don’t extend the capture session too long, otherwise the movement of Earth’s shadow will blur the edge more than usual.

Of course, the wild card will be the weather, which caused a lot of issues for much of the UK during the lunar eclipse in March. All we can do is keep our fingers crossed and hope for crisp, clear, haze-free skies this time around. Fortunately, with the final partial phase lasting just over an hour, there’s a decent window of opportunity to capture something worthwhile.

Equipment: DSLR or equivalent, mid- to long-focallength lens or telescope, remote shutter control, tripod

 Send your images to: gallery@skyatnightmagazine.com

STEP 1

Keep an eye on the weather and, if you’re prepared to put in a little extra effort, identify some alternative locations that might be clear in case you’re clouded out. Pick sites with unobstructed views in the required direction. From the centre of the UK, the Moon rises at azimuth 100° or just south (right) of east.

STEP 3

On evenings before the eclipse, focus your lens as accurately as possible on the Moon. Then, with the lens set to manual focus, use a length of low-tack electrical tape to secure the focus ring so it can’t rotate. When the Moon rises on 7 September, the show will already be under way, so you need to be as ready as possible.

STEP 5

Download your images and inspect their EXIF headers using freeware like FastStone. With a planetarium app, identify stars near the horizon and their azimuths by entering the shot’s date and time. Note the azimuths of visible horizon features. Using the same app, confirm where the Moon will rise on 7 September.

STEP 2

Choose your setup(s) and practise with the Moon on evenings ahead of the eclipse, especially if you intend to relocate on eclipse day. As a bare minimum, use a DSLR or equivalent with a 400mm or longer lens. Take your phone for atmospheric shots too, such as the Belt of Venus into which the Moon will rise.

STEP 4

To pinpoint exactly where the Moon will appear, visit your chosen location on a night before the eclipse. Wait for the sky to darken and Saturn to become visible. Set your camera’s clock accurately (ideally using UT), then take a wide or mid shot of the horizon where you expect the Moon to rise, exposing to capture stars.

STEP 6

On the night, set up in good time. Don’t be surprised if the Moon doesn’t show when expected: low haze can easily hide it. Binoculars will very helpful. Use a low to mid ISO and an aperture around f/8–f/11. Short exposures will capture the bright surface, but try longer ones to reveal colour in the shadowed regions.

Belt of Venus

Algenib

Alrescha

Saturn Water Jar

Expert processing tips to enhance your astrophotos

ASTROPHOTOGRAPHY

PROCESSING

Fix contrast extremes in your Moon shots

Use tone mapping to tame brightness and reclaim lost detail

BEFORE AFTER

Capturing night-sky objects comes with its fair share of challenges. How you handle them can make the difference between a good image and a great one. Sometimes, when everything conspires against you getting a clean shot, post-processing is your only solution!

For example, with some deep-sky, narrowband solar, or lunar images, parts of the frame will be very bright, while others will be darker and less defined. In lunar shots especially, details near the terminator can be particularly faint due to small shadows created by a low-angle Sun. These reduce the overall brightness in that part of the image. Because it only affects one area, it’s not easy to achieve an exposure that will reveal faint details without blowing out the brighter regions farther from the terminator.

This image of the southern highlands around Clavius (above) is a good example.

While the brighter areas are almost over-exposed, the capture settings were designed to prevent them from being completely blown out. However, the walled plain of Clavius on the left side of the image, where the Sun was rising, is still too dark.

This issue can only be fixed through processing. Affinity Photo, available for a one-off purchase price, has different workspaces for processing tasks, called ‘personas’, and its Tone Mapping Persona can address this processing problem. Tone mapping is designed to manipulate images to give them an extended dynamic range. It works best on flat and under-exposed images, lifting the brightness of the darker areas and helping to retrieve their detail. Here I’ll run through how you can use it effectively to improve your Moon images.

To begin with, open your Moon image in Affinity Photo, clicking File > Open. This

opens within the default Photo Persona workspace (see Screenshot 1). To access the Tone Mapping Persona, click the fourth Persona icon at the top left of the screen. As it opens, a progress bar will appear as the software will initially adjust the tonal range of your image. Don’t worry if afterwards the image looks overprocessed (see Screenshot 2).

Explore your options

There are several preset adjustments available down the left-hand side, but after clicking each of these you might find the results are too severe. Instead, you can make your own adjustments with the slider bars under the Tone Map tab on the screen’s right side (see Screenshot 3).

The two main sliders to use are Tone Compression, which is moved to the left, away from 100 per cent. As the adjustment is made, you should see a significant improvement in the tonal

 In Dave’s shot of the Moon’s southern highlands (left), crater Clavius was too dark, but he didn’t want to lighten everything and blow out the brighter regions. Using Tone Mapping Persona in Affinity Photo (right), he drew out detail while keeping the bright areas in check

3 QUICK TIPS

1. For the best results, begin with a shot that doesn’t have any completely blown-out highlights.

2. Tone mapping works on deep-sky and solar images too. Use it to reveal fainter details in these objects.

3. Less is more! Always apply settings that respect the data. Over-adjustments produce false artefacts.

range of your image. Adjust this to taste. Once you’re reasonably happy with the result, move the second slider, Local Contrast, to the right and away from 0 per cent. This adjustment is great for enhancing maria rays and wrinkle ridges in lunar images.

You may need to adjust both settings in small increments, one after the other, to find the best balance. In our case, we reduced Tone Compression to 32 per cent and Local Contrast to 28 per cent, brightening the darker lunar areas while keeping the sky background dark. The lunar details close to the terminator were then brighter and clearer, and shadows and features within the large walled plain of Clavius were more pronounced.

In the menu, beneath Tone Compression and Local Contrast are several other adjustment options, including Exposure, Brightness, Contrast and Saturation. Because our image was taken using a one-shot colour (OSC) camera, increasing the Saturation slider to 44 per cent brought out more colour in our image. The lunar surface has some very subtle colour variations, so it is always a good idea to try to tease these out.

Once you are happy with all your adjustments, click Apply in the top left to exit the Tone Mapping Persona tool. Your tone-mapped image will then reopen within Affinity Photo’s Photo Persona workspace. From here, you can fine-tune it further – sharpening, reducing noise, or adding final touches – before saving your beautifully enhanced Moon shot.

Dave Eagle is an astronomer, astrophotographer, planetarium operator and writer

 Screenshot 1: open your image in Affinity Photo, then click the fourth Persona icon (top left) to enter Tone Mapping. A progress bar will appear as tonal adjustments are applied

 Screenshot 2: a number of preset adjustments (such as Natural, Detailed, Cool) are offered down the left-hand side. Try them, but you may find the results are too drastic

 Screenshot 3: instead, experiment with incremental changes to the options on the right (including exposure, blackpoint, saturation and contrast). Once you’re happy, click Apply

Your best photos submitted to the magazine this month

ASTROPHOTOGRAPHY GALLERY

 The Clamshell Nebula

Nicole Poersch, Prestwick, South Ayrshire, UK, 15 September 2024–21 January 2025

Nicole says: “The Clamshell Nebula in Cygnus is often overlooked due to its proximity to the North America and Pelican Nebulae. It’s also very faint: this image required over 63 hours of exposure, spread over 22 nights.”

Equipment: ZWO ASI1600MM camera, William Optics Zenithstar 73 II refractor, iOptron CEM25P mount

Exposure: R 55x 40”, G 50x 40”, B 50x 40”, Ha 149x 600”, OIII 110x 600”, SII 113x 600” Software: PixInsight

Nicole’s top tips: “I began astrophotography in 2021, knowing it would take trial and error. I never imagined one of my photos would appear in a magazine, let alone win Photo of the Month! My top tips: believe in yourself, keep learning, be patient and don’t be afraid to share your work and ask for feedback.”

PHOTO OF THE MONTH

 Star trails

Greg Meyer, Ash Fork, Arizona, USA, 1 June 2025

Greg says: “This took a long time to process, and I’m still learning, but I love the effect of the 360° view, and the options that come with the processing.”

Equipment: Insta360 4X camera, Gitzo Mountaineer tripod Exposure: 500x 30” Software: Lightroom, StarStaX, Photoshop

The Spanish Dancer Galaxy 

Kfir Simon, Tivoli Farm, Namibia, 29–30 August 2024

Kfir says: “I love seeing a grand design spiral face-on, and the Spanish Dancer (NGC 1566) is a textbook example. The core was tricky due to its high brightness.”

Equipment: Moravian Instruments G361000 Pro camera, ASA 600 Ritchey–Chrétien, ASA DDM200 mount Exposure: L 30x 300”, RGB 4x 300”, Ha 6x 300” Software: PixInsight, Photoshop

 The Bubble Nebula

Jelieta Walinksi, St David, Arizona, USA, 21 June 2025

Jelieta says: “I overcame visibility challenges and monsoon clouds to reveal this stunning image. My appreciation for the Universe grows and makes me more curious about what else is out there.”

Equipment: ZWO ASI2600MC Pro camera, Celestron NexStar Evolution 9.25 Schmidt–Cassegrain, Sky-Watcher EQ6-R Pro mount Exposure: 30x 900” Software: PixInsight, DeepSkyStacker, Photoshop

 Moonrise

Peter Coates, Beverley, East Riding of Yorkshire, UK, 12–13 June 2025

Peter says: “I worked out the moonrise position the night before and was really pleased to capture this five-shot composite as the Moon slowly rose above Black Mill, a well-known local landmark.”

Equipment: Canon EOS 1100D camera, Canon 55–250mm lens, Zomei Z818 tripod

Exposure: 5x 0.5” Software: StarStaX

NGC 7822 

Kimberly Sibbald, Alberta, Canada, September and October 2024

Kimberly says: “NGC 7822’s striking question mark shape is a playful, poetic reminder that the Universe is always prompting us to keep learning, wondering and looking deeper into the unknown.”

Equipment: ZWO ASI2600MM Pro camera, Askar ACL200 refractor, Rainbow Astro RST-135 mount

Exposure: Ha 37x 20’, OIII 38x 20’, SII 28x 20’, total 34h 20’

Software: PixInsight, Photoshop

 IC 4633

Vikas Chander, captured remotely via Obstech, Rio Hurtado Valley, Chile, 28 June 2025

Vikas says: “Dust in space hides many secrets, but not all stay hidden! Here we see the spiral galaxy IC 4633 peeking through the dust of integrated flux nebula MW9.”

Equipment: Moravian Instruments C5A-100M camera, PlaneWave CDK24 astrograph, PlaneWave L-600 mount

Exposure: R 102x 300”, G 102x 300”, B 102x 300”, total 25h 30’

Software: PixInsight, Photoshop

Markarian’s Chain 

Overall Photons, 29 locations worldwide, March–May 2025

Overall Photons say: “Markarian’s Chain hides a secret: very faint bridges of ionised hydrogen linking the galaxies. Now, through the power of collaboration, these elusive structures have been captured in unprecedented detail.”

Equipment: 29 setups with telescopes ranging from 3 to 11 inches Exposure: 660h

Software: Siril, PixInsight, Photoshop

 M21

Massimo Di Fusco, captured remotely via Telescope Live, Rio Hurtado, Chile, 2 June 2025

Massimo says: “This open cluster was discovered by Charles Messier himself on 5 June 1764. It’s just 4.6 million years old and is home to over 100 stars.”

Equipment: QHY600PH-M camera, PlaneWave CDK24 astrograph, Mathis Instruments MI-1000/1250 mount

Exposure: R 2x 180”, G 2x 180”, B 2x 180”

Software: Astro Pixel Processor, PixInsight, Photoshop

 The Teddy Bear Nebula

Bill Lowry, Chiddingstone Hoath, Kent, UK, February 2025

Bill says: “I first shot the Teddy Bear with a one-shot colour camera a couple of years ago and wanted to now shoot it with my mono setup. The results make the extra effort worthwhile.”

Equipment: ZWO ASI2600MM Pro camera, William Optics GT81 IV refractor, Sky-Watcher EQ6-R Pro mount

Exposure: RGB 40x 30”, Ha 18x 20’, OIII 20x 20’, SII 23x 20’

Software: PixInsight

ENTER YOUR IMAGE

Whether you’re a seasoned astrophotographer or a beginner just starting out, we’d love to see your images. Send them to us at www.skyatnightmagazine.com/send-us-your-astrophotos

HOW WE RATE

Our experts review the latest kit

FIRST LIGHT

ED f/7 quadruplet refractor StellaMira 86mm

Pin-sharp stars, rock-solid build and easy imaging – we’re impressed

WORDS: IVANA PERANIC

• Price £1,199

• Optics Quadruplet refractor

• Aperture 86mm

• Focal length 602mm, f/7

• Focuser Dual-speed rack and pinion

• Extras Tube rings with finder clamp handle, Losmandytype dovetail, camera adaptors, two finder shoes, carry case

• Weight 5.8kg

• Supplier First Light Optics

• Email questions@ firstlightoptics. com

• www.firstlight optics.com

Earlier this year, First Light Optics announced a new addition to its in-house brand of telescopes, the StellaMira range. The 86mm f/7 quadruplet refractor is the first four-element telescope in the collection, with two extra-low-dispersion (ED) elements and a built-in flattener which promises a perfectly flat field of view, from corner to corner. It provides 602mm of focal length, which is perfect for a wide variety of popular targets, and – despite the rapidly disappearing darkness of our spring skies – we were excited to make the most of every clear moment to try it out.

The telescope is provided in a sturdy aluminium carry case, with a fitted foam insert to protect the refractor and its accessories. Out of the box, the quality of the build and all of the fittings is immediately obvious. The tube feels very solid without being heavy, while other elements are CNC machined, with no plastic in sight. There’s an integrated, retractable aluminium dew shield that extends with a twist motion, which we knew we would welcome in the humid evenings. We were also pleasantly surprised to see a Losmandy dovetail.

As is usual with First Light Optics’s own-brand telescopes, the StellaMira 86mm ED quadruplet comes with lots of small extras as standard. Apart from the carry case, these include not one but two finder shoes, M54 and M48 adaptors, and a carrying handle on top which doubles as a finderscope clamp. Even though this telescope is marketed as primarily for imaging, there’s a 2-inch-to-1.25-inch adaptor at the back that could take a diagonal and eyepieces for visual observation.

Getting started

To make the best of the last few hours of true darkness, we decided to test the telescope on a galaxy using our ZWO ASI2600MC Air camera. To attach the camera to the telescope, we had to first find a 1.5mm Allen key to detach the 2-inch-to-1.25inch adaptor from the back, which is held in place by

Dew shield

On the front of the StellaMira is a 123mm metal dew shield that can be extended and retracted with a twist motion. For an extra layer of protection against dew on very humid or damp nights, dew heaters can be easily attached behind the dew shield and front cell.

High-quality build

The body of the StellaMira 86mm ED refractor has a stylish and sturdy feel, with an aluminium tube, integrated dew shield and CNC-machined tube rings and handle. All the components feel solid without being bulky. The red anodised camera-angle adjuster and fine focuser are a lovely touch on the black tube.

Focuser

The focuser is a 3.2-inch dual-speed rack-and-pinion type, with 1:10 gearing – perfect for fine focusing. It provides a pleasingly smooth action that makes manual focus easy. On the back, there’s also a 360° camera-angle adjuster ring which rotates and can be secured by the metal thumbscrew.

FIRST LIGHT

Carry case

The telescope comes packed in a sturdy aluminium case with a top handle, making it an ideal travel companion for dark-sky seekers. Inside is a custom-shaped foam insert to keep the scope snug, as well as space for the accessories. For extra security, it comes with a key.

Losmandy plate

Unlike many of its counterparts on the market, the StellaMira 86mm ED comes with a Losmandy-type dovetail plate, which is wider than the more common Vixen type. This allows the telescope to sit on a flat surface with more stability, while it felt very secure and balanced on the mount.

Four-element optics

Inside the StellaMira 86mm quadruplet refractor are two extra-low-dispersion (ED) lens elements, with fully coated optics that deliver high contrast and minimal chromatic aberration. We were pleased to see both these characteristics were evident in our resulting images, which were crisp and detailed even under lighter skies. We were also impressed to note that the optics are bench-tested – that’s not always the case, so it’s worth highlighting.

The built-in flattener design of a quadruplet telescope not only corrects field curvature, but eliminates tedious back-focus calculations or the need for a separate accessory: simply attach your camera and focus.

This simplicity makes it an especially attractive option if you’re looking for your first astrograph and want a hassle-free introduction to imaging. It’s also appealing if you’re more experienced and aiming to simplify your setup and maximise precious imaging time. If you’d still like the flexibility of using a reducer, StellaMira offers an optically matched 0.8x reducer/flattener designed specifically for this telescope and keeps the flat field intact.



three small grub screws. This step may not be immediately obvious to first-time users, and there was no instruction manual or even a basic setup diagram to guide us. If components require screwing or unscrewing, the appropriate tool should be supplied. A brief manual would also help users who want to fit an electronic focuser, or switch between imaging setups.

Buttery-smooth focusing

When a clear night finally arrived, setting up the telescope proved quick and effortless. The built-in flattener meant we wasted no time making fiddly adjustments; instead, we simply had to plug the camera in and focus. This design will be greatly appreciated by all who, like us, need to make use of every minute and start imaging with no fuss. Focusing was also a speedy job. The rack-and-pinion focuser has a buttery-smooth action and there were no vibrations even when focusing manually.

Over the following nights, we aimed the telescope at M101, the Pinwheel Galaxy, as well as some star clusters. This gave us the opportunity to check stars across the frame – and we were genuinely impressed. There was no visible chromatic aberration, and star

 The Pinwheel Galaxy showed no chromatic aberration, 180x

shapes were round and tight. Under extreme scrutiny, we noticed a minuscule variation in the roundness of stars at the very edge of two corners, but this truthfully was not enough to warrant any attention.

During later imaging sessions, we were able to test out the optional extra to our setup: a 0.8x reducer/ flattener supplied by First Light Optics. It delivered excellent performance and, importantly, did so without compromising the built-in flattener – one of the telescope’s standout features.

We were left very impressed with the capabilities of this astrograph, especially considering its price point. The StellaMira 86mm ED f/7 quadruplet refractor would make the perfect winter companion for any astrophotographer.

VERDICT

 Passing the star test with flying colours, with open cluster IC4756 from 120x 30” exposures. All images were taken with a ZWO ASI2600MC Air on board

StellaMira reducer/ flattener 2. Electronic autofocuser

3. Filter wheel with filters

60”

Globular cluster M13 had round, tight stars from corner to corner, 120x 30”

Our experts review the latest kit

FIRST LIGHT

ON1 Photo RAW 2025.2 software

Skip the app-hopping rigmarole: edit and sort your shots in one streamlined space

WORDS: MARY MCINTYRE

VITAL STATS

• Price £90.37 one-off; free 30-day trail

• Features Editing, stitching, cataloguing

• Update Includes new AI-powered features for masking, sharpening and denoising

• System requirements (recommended) Windows 11 or MacOS 14 or above, eightcore Intel or AMD processor with 64-bit support, 16GB+ RAM, 6GB HD

• Developer ON1

• www.on1.com

While there’s no shortage of image-processing software out there, most programs excel at just a few aspects of astrophotography processing, leaving users to hop between multiple packages. This leads to complex – and increasingly costly – processing workflows, especially as more developers shift to subscriptionbased models.

ON1 Photo RAW 2025 brings together much of the functionality that’s typically spread across several well-known processing packages and combines it with cutting-edge AI-driven features into one piece of software – and all for a one-off purchase price. At the time of writing, the latest version was ON1 Photo RAW 2025.2, available on a free 30-day trial for curious imagers. We set out to see whether it could genuinely handle an astrophotographer’s entire workflow from start to finish.

The software downloaded easily, with no need to input payment details and so no risk of accidental charges. While many of ON1’s features cater to artistic image creation, there are also plenty of helpful tools for astrophotography processing. The interface is intuitive, especially if you’re used to other popular processing software, employing many of the same terms and conventions. But even if you’re new to image processing, don’t worry: there’s plenty of guidance to get you started (more on that later).



BEFORE

The editing process is non-destructive, so your original image remains untouched no matter how many changes you make. We also liked that there is a reset button, which makes it easy to start afresh if you need to.

ON1 claims to support raw files from over 800 camera models, as well as TIFF, JPEG, PSD, PSB, PNG, DNG and HEIC formats, and we met no issues with these. It doesn’t support FITS files, however, so we had to convert our 32-bit DeepSkyStacker TIFFs to 16-bit TIFFs before they would open.

The Develop module is where you’ll find the basic processing tools. Its Tone and Colour section applies linear histogram stretches (Levels), all controlled with sliders so you can see the effect on your image in real time. To perform multiple iterations of a linear stretch, you need to duplicate the layer, apply your changes, then merge the layer down to reset the sliders. You can also fine-tune colour temperature, tint and saturation here too. Sharpening and noise-reduction tools are included as well, and we found both delivered impressive results.

Exploring the effects

The Effects module includes other common functions, organised under the Filters menu. Select ‘Add filter’ to access options such as curves, colour balance and channel mixer, along with creative presets and effects such as HDR, border effects,

Impressive results with the Andromeda Galaxy. Trying out all sorts of edits is easy, without risking damaging your original data

 Salvage blurry shots with the AI-powered NoNoise and Tack Sharp tools – great for sharpening and denoising lunar craters

Super Select AI

The Super Select AI tool speeds up creating composite images as you simply click on an area to automatically select it. For example, we were able to quickly replace the blurred foreground of a stacked Milky Way image with the foreground from one of the single shots, producing a sharper result.

Learning library

ON1 has a vast library of over 1,000 excellent, clear and concise video tutorials. The Quick Start learning hub will teach you the basics, but hovering the mouse over each tool will pull up a ‘learn how’ link to the relevant video. There are also nearly 50 written guides available.

FIRST LIGHT

Tack Sharp AI

Tack Sharp AI is ON1’s tool for sharpening blurred or slightly out-offocus images. Located in the Noise & Sharpening section of the Develop module, it uses AI-driven technology to analyse and apply sharpening to your image, before generating a preview.

You can then drag a divider across your image to compare the ‘before’ (left side) and ‘after’ (right side) views. If the results look over-sharpened, you can fine-tune the effect using the sliders to adjust deblurring and micro-sharpening.

Panorama stitching

Stitching images together into a panorama is easy. Select your chosen images from the browser menu, then click the Panorama icon on the right-hand tool bar. Check the preview that is generated, then click the blue tick. The process works best if a lens distortion correction is applied to each image first.

This tool can take a while to run, so it’s worth checking the status bar to ensure the preview has fully loaded before making further adjustments.

Once you hit ‘Apply’, it may take a few minutes to finish sharpening. We saw

particularly impressive results with lunar crater images and sunspot photos captured in both white light and hydrogen-alpha. Tack Sharp AI can also be used alongside the NoNoise AI tool to apply smoothing at the same time.

After using the built-in panorama-stitching feature

Eraser tools

There are some excellent eraser tools in ON1. Perfect Eraser removes sensor dust or powerlines with one click, and Generative Eraser allows you to remove unwanted foreground objects. Simply draw over the object with your mouse and the software will remove it and fill the gap with natural-looking detail.

NoNoise AI

ON1’s NoNoise AI uses algorithms to analyse your image and figure out the optimum amount of noise reduction without losing detail. You can slide the divider side to side to see the results before hitting ‘Apply’. This tool may take a couple of minutes to run.

tilt-shift effect, and more. There’s an option to only apply these changes to certain parts of your image, which is helpful if, for example, you want to exclude the foreground while enhancing detail in a nightscape sky.

Beyond the basic processing tools, there are numerous advanced tools, such as composite creation, batch processing, panorama stitching and even focus stacking. ON1 has a suite of AI-driven and automated tools that can help to take some of the legwork out of your post-processing. We found these tools took a minute or two to run, so a little patience is required. The software also offers image cataloguing and organisation, and the ability to add keywords to your images, making it easy to search your library later.

We tested ON1 with a range of images – including the Sun, Moon, deep sky and the Milky Way – and with creating panoramas, and found it delivered pleasing results across the board. The built-in

‘learning library’ of resources makes it easy to get to grips with the basic and advanced tools, which is helpful for beginners and experienced users alike. ON1 can run as a plug-in for Photoshop or Lightroom, but there are so many features packed into this software that it could easily be used as a standalone solution.

The very reasonably priced one-time purchase model may appeal to those keen to avoid ongoing subscription costs, and the 30-day trial provides a risk-free way to explore what it offers.

VERDICT

Charlotte Daniels rounds up the latest astronomical accessories

GEAR

1 Altair Sentinus all-sky camera dome housing

Price from £115 • Supplier Altair Astro www.altairastro.com

Capture meteors, star trails or timelapses with this customisable all-sky camera dome. UV-resistant and rainproof, it can house a range of cameras and lenses, plus a mini PC or Raspberry Pi. You can opt to add a streetlight shroud or dew heater if needed.

2 Solar pebble light

Price £24.99 • Supplier SolarCentre www.thesolarcentre.co.uk

We think a few of these 24cm x 32cm solar-powered pebbles could be an astronomy-friendly way to light your garden. Simply pick the red option on the remote control and you’ll be able to find your way to your equipment without ruining your dark-adapted vision.

3 Meteorite cufflinks

Price £159 • Supplier Hepburn and Hughes www.hepburnandhughes.com

These sterling-silver cufflinks contain fragments from the Swedish Muonionalusta meteorite that impacted northern Scandinavia and was first discovered near Sweden in 1906. Presented in a smart box, you’ll be gifting a piece of cosmic history.

4 Astronaut socks

Price £33 • Supplier The London Sock Exchange • www.thelondonsockexchange.net

This is a set of three pairs of socks knitted from sustainably sourced melange cotton, each featuring a space-themed design, including astronauts, space shuttles and even a nod to the Hubble Space Telescope. Available in sizes 7–12.

5 Houdini 20mm 86° coma-correcting eyepiece

Price £339 • Supplier First Light Optics www.firstlightoptics.com

This ultra-wide eyepiece brings something new to the table: built-in parabolic coma correction removes the need for a coma corrector on Newtonian telescopes. Purpose-built for parabolic mirror systems as fast as f/4, it can also work on any scope of f/6 or slower.

6 Voyage fountain pen

Price £135 • Supplier Cult Pens

www.cultpens.com

Fountain pens might not work in space, but Earthbound astronomers will appreciate the galactic-grey shimmer of this cosmos-inspired design. With a stainless-steel nib, screw-on cap and fine engraving, it would make a lovely gift for any stargazing scribe. 5 4 6 3 2 1

New astronomy and space titles reviewed

BOOKS

111 Places in Space that You Must Not Miss

Mark McCaughrean Emons Verlag

£13.99  PB

Perusing the shelves of your local bookstore, you’ll no doubt find a vast selection of guidebooks highlighting must-see attractions in cities and countries around the world, demonstrating our species’ obsession with travel. This latest entry in the 111 Places series from publisher Emons Verlag takes a break from the Earth-bound and instead presents the most interesting attractions to be found beyond the confines of our home planet.

on information beamed back by observatories and, for some more local destinations, visiting spacecraft.

Whittling the Universe down to just 111 places is a tall order and, as with any guidebook, the list is inevitably subjective. An assortment of fascinating destinations is included, starting within our Solar System before moving out to the farthest reaches of observable space. Magnificent images and informative descriptions of the attractions are included, as well as details of their location, how to get to them (assuming the technology exists) and tips on how to make sure you get all you can out of your trip. McCaughrean’s striking and insightful descriptions of the sensations a visitor might see or experience at some of these locations are particularly captivating.

Olympus Mons on Mars, one of the wonders in McCaughrean’s cosmic travel guide

Unusually for this series, only one entry (the Moon) has actually felt the small steps of humanity, and so author Mark McCaughrean instead picks places of interest from across the Universe, based

Given the already tight limit on the number of places, I was disappointed to find cases in the Solar System section where a whole object and individual locations on that same object are listed as separate entries. For example, Mars appears as location 21, while entries 9, 11 and 27 are the dust devils on Mars, the so-called ‘face on Mars’ and Olympus Mons, the largest volcano on Mars (and, for that matter, in the Solar System). Had each body featured only once, with separate attractions on them included in that entry, perhaps more wonders of our Solar System could have occupied the additional space.

Nevertheless, this is a wonderful concept and an interesting, enjoyable read. A fine addition to the (jet) backpack of any budding astronaut. ★★★★★

Penelope Wozniakiewicz is a senior lecturer in space science at the University of Kent

Interview with the author Mark McCaughrean

Where in the Solar System would you love to visit?

The active volcanoes on Venus and Io, as well as the cryovolcanoes of Triton, would be exciting to see. The subsurface oceans of Jupiter and Saturn’s icy moons hold great fascination, as does the cratered surface of Saturn’s moon Hyperion, which may have caves inside. A visit to comet 67P would be emotional – to see those landscapes we’re so familiar with and to see our old robot lander friends once again.

Should we be sending humans to the Moon and Mars?

I’m ambivalent about it. Making the long journey to Mars and back would be a huge achievement. But the agenda is increasingly set by people who are interested in colonisation, exploitation and self-aggrandisement. Given the role those have played in the rapidly declining state of this planet, I’ve little enthusiasm for seeing it continue elsewhere.

What Solar System mysteries remain?

A crucial one is how life arose on Earth and whether it exists elsewhere in the Solar System, in similar environments to the young Earth, like Mars, or utterly different, like Titan. But as someone who studies the birth and evolution of stars and planets elsewhere, the search for clues about the early stages of our Solar System is interesting. Were we born in a dense cluster, surrounded by other stars? Were there more planets and planetesimals initially, and how was the Solar System ‘rearranged’ by cataclysmic events?

Mark McCaughrean is a space scientist and science writer

The Astronomy Handbook: A Field Guide to the Night Sky

£6.99  PB

How do kids – or anyone, for that matter – get hooked on astronomy?

Seeing the Moon’s craters through binoculars or spotting the ‘W’ of Cassiopeia for the first time can spark a lifelong interest. That’s the world that The Astronomy Handbook aims to open up to readers aged eight and over.

The book pledges to guide the reader through this rich landscape, promising, “once you’re hooked, the night sky’s the limit”. In less than 100 pages of bite-sized text and simple, clear illustrations, it runs through everything you need to know.

What I enjoyed most was its mix of the extremely practical with fascinating tales. For example, did you know that Roman soldiers could become archers only if they could see Ursa Major’s Mizar and Alcor as separate stars?

Like many children’s astronomy books, this starts in prehistory, with the pyramids and stone circles of Mesolithic times that marked solstices and equinoxes, revealing humanity’s early fascination. It then sweeps through history: from the ancient Egyptian star goddess Sopdet to fifthcentury Indian astronomer Aryabhata, who suggested that it’s Earth that spins, rather than the stars that move around it; to Galileo and the moons of Jupiter; to Edwin Hubble identifying Andromeda as the first galaxy beyond our own; to the Space Race and the modern day.

From here, the book launches into its comprehensive stargazing guide. It covers the nitty-gritty, from the naming and magnitude of stars, to how to choose and

use binoculars and telescopes. It gives the lowdown on 17 key constellations, with attractive illustrations and consistent page furniture by Rhys Jefferys that kids will appreciate. Each includes a ‘Story from the stars’ box, sharing the classical myths behind the names.

Our Solar System is similarly covered, including planetary vital statistics that will delight fact-collecting readers, such as volume comparisons to Earth and cloud-top temperatures. And if you enjoy a list, the book explains the Messier Catalogue, as well as providing its own pick of top 10 sights to observe, such as the Moon’s surface and the Orion Nebula.

If this book set out to hook young readers and enable them to get full enjoyment of the night sky, it certainly goes a long way towards achieving that.

Shaoni Bhattacharya is a science writer and editor

The Moon: From Imagination to Exploration

Various authors

DK

£25  HB

Few celestial bodies have captured the human imagination quite like the Moon, and this book delivers a beautifully crafted tribute to Earth’s nearest neighbour.

With a foreword from seasoned astronomer and author Adrian West, and contributions from six science writers – including archaeoastronomer Carolyn Kennett and astronomer Philip Eales – this book orbits gracefully through the Moon’s scientific history, its enigmatic surface and the ever-evolving story of human lunar exploration.

Dorling Kindersley has a knack for producing informative, colourful and

engaging books crammed with facts on every page. I’ve loved their titles since I was young, and now, even into my 40s, this latest work – written in association with the Smithsonian Institution – holds the same appeal.

The eye-catching cover sparks curiosity, setting the stage for a deep dive into the Moon’s real story. The 256 pages of this hardback are divided into beautifully illustrated sections, offering a rich tapestry of science fact that spans the birth of the Moon, ancient lunar observations and the scientific revolution, from the invention of the telescope to early lunar maps.

Leaving no Moon rock unturned, the reader is taken on a journey through humanity’s enduring fascination with our satellite, including the race to space and the Apollo Moon landings. The book also explores the latest advancements in lunar exploration and plans for future Moon missions, including ambitions to build a permanent base on its barren surface and mine its resources.

Its blend of easy-tounderstand diagrams, full-colour photos and accessible explanations makes any of the more complex ideas simple to grasp, whether discussing lunar seismic activity or the technology used to land Apollo’s crewed missions.

The directory at the end of the book is well presented, offering keen beginners a guide to observing the Moon, with details of the lunar phases and key features to look out for on its Earth-facing side.

The Moon: From Imagination to Exploration is an illuminating and visually engaging guide that truly honours the Moon’s place in both science and culture. Ideal for young and adult stargazers alike, it’s a must-read for anyone ready to take one small step into lunar science.

Katrin Raynor is an astronomy writer and communicator ONE FORMOON FANS!

William Potter and Rhys Jefferys Arcturus

Anita Chandran talks to Dr Itziar de Gregorio-Monsalvo

Q&A WITH AN ASTROPHYSICIST

Light pollution is a growing threat worldwide. Now astronomers are battling an industrial project in Chile that could compromise some of Earth’s darkest skies

What makes Chile, specifically the Atacama Desert, a prime location for looking at the cosmos?

Chile is the best place on Earth for doing astronomy in different wavelengths. We have very clear and quiet skies, which are perfect for observations in the optical and infrared. We also have high, dry places in the mountains which are good for ‘millimeter’ and ‘submillimeter’ astronomy. Observing sites like the European Southern Observatory (ESO) Paranal site are in the middle of the Atacama Desert, far from big cities and their associated light pollution.

What exactly is light pollution?

It’s the brightening of the sky caused by the excess light that we human beings emit into the atmosphere. We emit a large amount of unnecessary light – say, from poorly positioned streetlamps and the blue light component of LEDs – which can brighten the sky far away from the pollution’s source.

How does it affect astronomy?

It limits our ability to look deep into the Universe, particularly using optical astronomy. When we observe with a telescope, we can’t differentiate light coming from the cosmos and light coming from light pollution. So we can’t see very faint objects, such as Earth-like planets close to other stars.

What is threatening the quality of skies over ESO sites in Chile?

We’re being exposed to threats from industrial projects close to our Paranal observatories – huge projects, almost like mini cities, that require large amounts of light for safe operation. One such project, INNA, which is a green hydrogen site, would sit very near the proposed south site of the Cherenkov Telescope Array Observatory (CTAO-South).

Could that have a wide impact at Paranal?

Yes. The blue photons that CTAO-South would observe are extremely sensitive to light pollution that we expect the INNA project will cause. The project will also rely on a wind farm for energy, which is likely

 The pristine skies above Paranal remain among the darkest on Earth – but a large-scale nearby project might change that

to shake the ground and cause vibrations that will impact the sensitive mirror alignment of the upcoming Extremely Large Telescope (ELT) and the interferometer VLTI. The wind farm and solar plant will also contribute to increased atmospheric turbulence, which will be difficult to correct for and will damage the quality of our optical images. That’s to say nothing of the construction phase and the associated dust and vibration.

What steps has ESO taken in response to the proposed project?

We’ve been calculating the impact of the INNA project and found that if they move to a safe distance away, the damage from vibrations and light pollution would be minimised. We’ve submitted our proposals to the Chilean government as part of the project’s review process. This will take time, but Chile is committed to protecting the quality of its dark skies – that’s been the case for more than six decades.

How is ESO tackling the wider challenges of light pollution?

ESO works with the regional government of Chile and collaborates with other international observatories to reduce light pollution. We also raise awareness so that authorities and the public understand why they should protect the quality of the skies.

Why should we care about light pollution?

Astrophysicist

Itziar de GregorioMonsalvo is the European Southern Observatory (ESO)’s representative in Chile

Dark skies are important for humanity because they’re the last windows into the Universe. If you live in a big city, at some point you’ll no longer see the stars or the Milky Way. You’ll lose connection with the Universe. On a practical level, the technology we use in astronomy also benefits humanity – take the digital camera, for example. This progress will stop if we lose our power to observe the Universe.

How can people get involved?

It can start from very basic steps, like changing the lighting outside your house, through to more involved measures, like talking to your local government about what they’re doing to tackle light pollution.

(EQ1)

f/7.8

THE SOUTHERN HEMISPHERE

With Glenn Dawes

Set your alarm and enjoy a prime view as the Moon slips into Earth’s shadow – a total lunar eclipse

When to use this chart

1 Sep 00:00 AEST (31 Aug, 14:00 UT)

15 Sep 23:00 AEST (13:00 UT)

30 Sep 22:00 AEST (12:00 UT)

SEPTEMBER HIGHLIGHTS

On 8 September, a total lunar eclipse is visible across Australia. The partial phase begins at 02:27 AEST (00:27 AWST), reaching totality at 03:31 AEST (01:31 AWST). Earth’s shadow covers the whole Moon until 04:53 AEST (02:53 AWST), with the partial phase ending at 05:57 AEST (03:57 AWST). It will be a moderately dark eclipse, the northern limb of the Moon reaching the shadow’s centre, mid-eclipse, at 04:12 EST (02:12 AWST) and the southern limb remaining slightly brighter.

THE PLANETS

The early evening finds Mars the solitary planetary offering, low in the west and setting about an hour after twilight ends. On the 13th, it passes just 2° from Spica. Saturn and nearby Neptune are at opposition this month, rising near

DEEP–SKY OBJECTS

This month, a trip to Capricornus. At the western end of its roofshaped asterism lies a brilliant naked-eye double star, Alpha (α) Capricorni (RA 20h 18m, dec. –12° 33’). This mag. +3.8 and +4.2 yellow pair are 6 arcminutes apart. Include nearby Beta (β) Capricorni (2.3° south-southeast) to see a double-double star! Beta has mag. +3.0 (yellow) and +6.0 (white) components, 3.3 arcminutes apart. A small scope reveals Beta is actually a

The chart accurately matches the sky on the dates and times shown for Sydney, Australia. The sky is different at other times as the stars crossing it set four minutes earlier each night.

STARS AND CONSTELLATIONS

Many northern constellations trace their origins back over two thousand years, rooted in ancient myths. Those deep in the southern sky were formalised much later. The 18th-century French astronomer de Lacaille named several, inspired by the scientific instruments of his time. Earlier, in 1598, Dutch cartographer Plancius’s theme was exotic birds – some visible this month, such as the striking Grus the Crane, and Pavo the Peacock, Tucana the Toucan, and Phoenix.

sunset and due north and highest around midnight. Uranus arrives in the late evening, transiting near dawn. Jupiter rises around 03:00 mid-month, followed by radiant Venus, which remains low in the eastern dawn glare.

triple, with a mag. +9.0 star 3.7 arcminutes from the brightest member, together all forming a dog-leg shape.

Capricornus also hosts the fine globular cluster M30 (RA 21h 40.3m, dec. –23° 11’). This seventh-magnitude cluster has a broad (4-arcminute), evenly bright core with a twinkling of stars, surrounded by a narrow, irregular halo thinning into the surrounding star field.