Image Of The Month
Image courtesy of: Pete Williamson FRAS - Member of the Online Astronomy Society.
Image of the Month Astronomer Biography of the month 25 year old planet forming mystery m,ay have just been solved Review of Brown Dwarf numbers Things to see August 2017 - Night sky diary Space Kidets Scientists observe gravitational waves for the second times On the Magnetic Protection of the Atmosphere of Proxima Centauri b The Resilience of Life to Astrophysical Events
Astronomer of the Month - Biography 10th August 2017 is the anniversary of the birth, at Mendon, Ohio on 10 Aug 1862, of the American astronomer William Joseph Hussey. A graduate of the University of Michigan he served as assistant in the Nautical Almanac Office of Washington before joining the faculty of Stanford University as professor of astronomy in 1892. He was Astronomer at the Lick Observatory from 1896 before returning to the University of Michigan in 1905 to become director of the Detroit Observatory. His contributions to astronomy include a series of valuable measurements of planetary satellites, particularly of the satellites of Saturn, as well as of the orbits of minor planets and comets. However, he is probably best remembered for his observations of double and binary stars. During his time at Lick Observatory he worked with fellow astronomer Robert Grant Aitken in a comprehensive survey of these objects, discovering and measuring 1,327 close double stars prior to his return to Michigan in 1905.
25 Year Old Planet forming Mystery may have just been solved! Ever since the first exoplanet was discovered 25 years ago, a fundamental question has remained unanswered. How could a planet form in close proximity to a neutron star? Research conducted by Dr Jane Greaves at the University of Cardiff and Dr Wayne Holland at the UK Astronomy Technology Centre in Edinburgh may have at last solved the mystery. Neutron stars are tiny, super dense objects which are the remnants of a supernova explosion of a star many times more massive than the Sun. Despite the fact that the first ever exoplanet discovered was in orbit around a neutron star, these planets have turned out to be incredibly rear bodies. Since a supernova explosion would destroy any pre-existing planets within the star system, how they form has been a mystery. In order to form new planets, the neutron star would need to capture new material in sufficient quantities to form a planet. These after-death planets can be detected because their gravitational pull alters the times of arrival of radio pulses from the neutron star, or 'pulsar', that otherwise pass us by extremely regularly. The research conducted by Greaves and Holland suggests they may have found a way for such planets to form following a supernova. Greaves states "We started looking for the raw materials soon after the pulsar planets were announced. We had one target, the Geminga pulsar located 800 light years away in the constellation of Gemini. Astronomers thought they'd found a planet there in 1997, but later discounted it because of glitches in the timing. So it was much later when I went through our sparse data and tried to make an image."
A false colour image of the Geminga pulsar (shown inside the black circle), moving towards the upper left of image. The orange dashed arc and cylinder show the “bow-wave” and a “wake”. Credit: Jane Greaved / JCMT / EAO. Using the James Clerk Maxwell Telescope (JCMT) in Hawaii, Holland states "What we saw was very faint. To be sure, we went back to it in 2013 with the new camera our Edinburgh-based team had built, SCUBA-2, which we also put on JCMT. Combining the two sets of data helped to ensure we weren't just seeing some faint artefacts."
A sketch of the nebula formed by a wind of electrons and positrons coming from the pulsar, and the interaction with interstellar gas. Credit: Jane Greaves / University of Cardiff. Both images showed a signal towards the pulsar, plus an arc around it. Greaves adds: "This seems to be like a bow-wave – Geminga is moving incredibly fast through our Galaxy, much faster than the speed of sound in interstellar gas. We think material gets caught up in the bow-wave, and then some solid particles drift in towards the pulsar."
According to calculations conducted by Greaves, it is suggested that this trapped interstellar 'grit' adds up to at least a few times the mass of the Earth. This therefore could provide sufficient raw material to form further planets, post-supernova. Although more data is still required to produce an image of higher definition, Greaves has already applied for time on the Atacama Large Millimetre Array (ALMA) to yield greater detail. It is hoped that the increased resolution will show the raw material orbiting around the pulsar. If this is indeed the case, and the ALMA data is able to conform the model for Geminga, the team plan to study further pulsar systems. If planets can form in such exotic environments, this will certainly contribute to the theory that planet birth is commonplace throughout the universe! Andrew Richens, FRAS
Review of Brown Dwarfs Numbers (Andrew Richens) A recent study conducted by Koraljka Muzic from the University of Lisbon and also Aleks Scholz from the University of St Andrews has cast new light on the numbers of brown dwarf stars which populate our Milkyway galaxy. Their study suggests that these stars are more abundant that first thought, with perhaps more than 100 billion inhabiting our Galaxy. Brown dwarfs are objects intermediate in mass between stars and planets. Unlike our own star, the Sun, their mass is too low to sustain stable hydrogen fusion within their core. As a result, brown dwarfs are cooler, dimmer and, subsequently, harder to detect. First discovered in 1995, it is now know that these objects are a natural by-product of the same processes that primarily lead to the formation of stars and planets. However, of the many thousands of brown dwarfs already catalogued, the vast majority are located relatively close to home due to the difficulties in detecting such faint objects. Furthermore, most of these detections have occurred within nearby star forming regions. These are fairly small patches and exhibit low star densities. The team began their research over ten years ago. In 2006, five nearby star forming regions were studied in the Substellar Objects in Nearby Young Clusters (SONYC) survey. If was found that clusters such as NGC 1333 possessed half as many brown dwarfs as they did stars. This was a high proportion than had previously been observed. In 2016, the team endeavoured to establish if the brown dwarf/star ratio within NGC 1333 was typical of other clusters. They chose to study the cluster RCW 38. This cluster is very unlike NGC 1333 in that it has a high density of more massive stars. Furthermore, at a distance of 5500 light years (compared to 1000 light years to NGC 1333), brown dwarfs would be fainter and harder to detect amongst the brighter stars.
False-colour near-infrared image of the core of young massive cluster RCW 38. The field of view of central frame is approximately 1 arc minute, or 1.5 light years across. Image: ESO’s Very Large Telescope (VLT) Muzic and Scholz detected just as many brown dwarfs in RCW 38 – about half as many as there are stars- and realised that the environment where the stars form, whether stars are more or less massive, tightly packed or less crowded, has only a small effect on how brown dwarfs form. Scholz says: "We've found a lot of brown dwarfs in these clusters. And whatever the cluster type, the brown dwarfs are really common. Brown dwarfs form alongside stars in clusters, so our work suggests there are a huge number of brown dwarfs out there." Based on the results from the SONYC survey, Scholz and Muzic estimate that the Milky Way has a minimum of between 25 and 100 billion brown dwarfs. They also suggest that because there are many smaller, fainter brown dwarfs that would not have been detected, this number could be a significant underestimate. Their survey confirms that brown dwarfs are numerically abundant!
An artist’s impression of a T-type brown dwarf. Credit: NASA / JPL-Caltech
Astronomy Things To See During August 2017 (For UK Observers) Moon: Full: Last Quarter: New: First Quarter:
7th August 7:10pm 15th August 2:15am 21st August 7:30pm (slight partial solar eclipse visible at sunset from the UK) 29th August 9:13am
The Lunar “X” and “V” are visible at around 08:00 UT which is several hours before the Moon rises, so we can’t observe them from the UK this month
Lunar conjunctions & occultations: Note: When the Moon is waxing it is visible in the western sky after sunset. When near Full Moon it is visible most of the night. When it is waning, it is visible in the eastern sky before sunrise 1st August Waxing Gibbous Moon lies close to Beta Scorpii & Antares 2nd/3rd August Waxing Gibbous Moon lies close to Saturn th 9 August Waning Gibbous Moon lies close to Neptune & Lambda Aquarii 13th August Waning Gibbous Moon lies close to Uranus 14th August Waning Gibbous Moon occults Xi2 Ceti th 15 August Last Quarter Moon occults 5 Tauri th 16 August Waning Crescent Moon occults some bright stars in the Hyades cluster 18th August Waning Crescent Moon lies close to Alhena th 19 August Waning Crescent Moon lies close to Venus & Ceres 24th August Waxing Crescent Moon occults Porrima th 25 August Waxing Crescent Moon lies close to Jupiter & Spica 27th August Waxing Crescent Moon lies between Alpha & Beta Librae th 29 August First Quarter Moon lies close to Antares & Saturn 30th August Waxing Gibbous Moon lies close to Saturn again
Planetary Observations: Mercury – is not easily observable this month Venus – rising at around 2:30am at the start of August (around 3am by the end of the month), mag -3.9 Venus dominates the predawn sky as it moves through Gemini. On 2nd August it will just 2.5 degrees from the open cluster M35. On the morning of 19th August, the Waning Crescent Moon lies very close to Venus. On 25th August, Caster and Pollux lie directly above it. On 31st August, Venus lies just 2.2 degrees from M44 the Beehive Cluster Mars – is not easily observable this month Jupiter – located in Virgo, Jupiter is visible in the west after sunset and sets at around 10pm. At mag -1.7 it should be easy to spot amongst the faint stars of Virgo. On 12th August, Jupiter lies close to Theta Virginis, and on 25th August the Waxing Crescent Moon lies close to Jupiter & Spica Saturn – located in Ophiuchus, Saturn is visible low in the south after sunset and sets at around 1am. Its magnitude this month is +0.4 which isn’t especially bright, but with good binoculars or a small telescope you will have no trouble seeing Saturn’s rings. On 2nd and 3rd August, the Waxing Gibbous Moon lies close to Saturn and on 29th & 30th August the Waxing Gibbous Moon again lies close to Saturn Neptune – located in Aquarius, Neptune rises at around 9pm. At mag +7.8 you will need binoculars or a telescope to spot it Uranus – located in Pisces, Uranus rises at around 10pm. At mag +5.8 you will need binoculars or a telescope to spot it. On 13th August the Waning Gibbous Moon lies close to Uranus Pluto – located in Sagittarius, Pluto is visible low in the south after sunset and it sets at around 3am. At mag +14.2 you will need a large telescope to spot it
Ceres – located in Gemini, Ceres rises at around 3am and remains visible until the dawn twilight. On 4th August, Ceres lies close to Epsilon Geminorum. Between 9th and 14th August, Ceres lies very close to Venus, and on 19th August, the Waning Crescent Moon also lies nearby, making an excellent photo opportunity Vesta – is not easily observable this month Pallas – during its brief apparition for 2017, Pallas is visible throughout August and the first half of September. Moving from Cetus into Eridanus this month, it rises in the east at around 1am and remains visible until it becomes lost in the dawn twilight. It will be around mag +8 during August so you will need binoculars or a small telescope to spot it Flora – becoming visible during the 2nd half of August, Flora is a dawn object located in Taurus. It will get brighter later in the year, but during August it will be mag +9.4 so you will definitely need good binoculars or a small telescope to spot it
Other Observations:. Noctilucent Cloud Season Comes To An End – although the peak of NLC season is during June & July, you may still see NLCs during the first half of August. At an altitude of around 8 times higher than other clouds, they are right on the edge of space. If visible, they can be seen around 60 – 120 minutes after sunset in the north west or 60 – 120 minutes before sunrise in the north east, but only between the end of May and mid August. They appear to glow a gorgeous white/blue whilst all the other clouds are in shadow, giving them their name “night shining clouds”. They are unpredictable, but if you get a good display, you will agree that they are well worth staying up late or getting up early for! Perseid Meteor Shower – one of the highlights of our astronomical calendar, the Perseid meteor shower is active from 23rd July until 20th August, with the peak of the shower falling on Saturday night of 12th/13th August. Under ideal conditions you can expect to see around 30 meteors per hour, but this year we have the Gibbous Moon (just 5 days past full) bleaching the sky so it will be difficult to spot the fainter meteors. However, don’t let that stop you from going and observing because brighter meteors will still easily punch through the moonlight. The radiant of the Perseids is close to the border between Perseus/Cassiopeia/Camelopardalis, quite close to the Double Cluster. But that doesn’t mean you need to watch that area to see meteors, as they can appear anywhere in the sky. In fact, your best chance will be to look north towards Ursa Minor and Ursa Major, the opposite side of the sky from the bright Moon. If you want to try and photograph the shower, point your camera about 30-40 degrees away from the radiant and about 45 degrees up (to avoid low light pollution and haze). And be very wary of highly exaggerated press articles claiming that this will be the best meteor shower for over a hundred years! Multiple Lunar Occultations – As you will have seen in the list above, there are several stars occulted by the Moon this month. 13th/14th August, at 00:55 BST, Xi2 Ceti will emerge from the shadow limb of the Moon 15th August just before 04:50 BST, 5 Tauri will emerge from the dark limb of the Last Quarter Moon 16th August – between 02:35 BST and 07:39 BST, several bright stars from The Hyades Cluster are occulted. The final star to be occulted is Aldebaran, which disappears at 06:42 BST and emerges at 07:39 BST. Although this takes place in daylight, it will be easy to observe with a telescope 24th August – 21:00 BST Porrima will disappear behind the shadow side of the Waxing Crescent Moon as they both set in the west. Please note: Exact timings of these events will vary according to your latitude, so check Stellarium, or your copy of Astronomy Now or Sky at Night Magazine for exact timings for your location Partial Solar Eclipse – you must’ve been living in a cave if you haven’t heard about the total solar eclipse visible across North America on 21st August by now! However, you may not have realised that a partial eclipse is visible from the UK near to sunset. The Moon’s shadow can be seen partially covering the Sun’s lower edge from around 19:40 BST until the Sun sets at around 20:22 BST. Please do not attempt to view this event without the correct solar observation equipment. If you don’t have access to proper eclipse glasses or have a solar filter for your telescope, you can use a projection method to observe it instead. But make sure you follow the instructions carefully if you do this! Minor Planet Florence Flyby – Minor Planet 3122 Florence will reach binocular visibility towards the end of August and into the beginning of September. On 31st August it will be at its brightest, but reaches its closest point to Earth the next night as it passes from Aquarius into Delphinus. It is thought that Florence is 4 km in diameter so as it passes within 8 million km of Earth it will be unusually bright, peaking at around mag +8.7 which is easily within binocular range. See if you can observe it over multiple nights and plot its movement relative to the background stars
Milky Way – August is a great month for observing the Milky Way as we start to get more hours of darkness. This gives us the opportunity to observe the region around Scorpius and Sagitarrius, which are absolutely packed full of deep sky objects which are easy to find. For more details about what you see in this region, take a look at Night Scenes 2017 by Paul Money Binocular Tour – This month’s Sky at Night Binocular Tour by Stephen Tonkin is focused on the sky around Cephus. There are 2 objects to spot if you have 15 x 70 binoculars. The first is the double star OΣΣ. You can resolve the double in much smaller binoculars, but 15 x 70s will really show the colour contrast between the two stars, one being very orange/red, the fainter one yellow/white. Next look for NGC 7160. Set within a small open cluster, this contact binary pair contains the slightly variable EM Cehphei. There are 4 further objects to look for with 10 x 50 binoculars. First is Delta Cephei. This famous star varies in magnitude from +3.6 - +4.5 with a period of 5.37 days. The star itself is a double which can be resolved with binoculars, with the brighter one a deep yellow colour and the secondary a fainter, white star. Next is Herchel’s Garnet Star, Mu Cephi, so named for its deep red colour. If you have a dark, transparent night, see if you can find IC 1396, a mag +3.5 open cluster. It is easier to spot at low magnification, but if you have larger binoculars, try holding up a UHC filter to eye piece to help see the nebulosity. Finally, is NGC 7243, an open cluster set within a beautiful part of the Milky Way. For full details on how to find these objects, look at this month’s edition of Sky at Night Magazine Deep Sky Tour – This month’s Sky at Night Deep Sky Tour is centred on the area around Sagitta. There are 3 planetary nebulae here; M27 the Dumbell Nebula, NGC 6886 which is much smaller than M27 but still quite bright, and NGC 6905 which is similar in magnitude to NGC 6886 but is much larger. All three objects are best viewed through moderately sized telescopes. There are 2 open clusters in this region, first is NGC 6830. A 6” telescope will resolve around 15 stars, the brightest of which form a diamond shape within another diamond! A 10” telescope will resolve double that number of stars. The other open cluster is Harvard 20, which is very small and sparse and can be difficult to spot! A 6” telescope will resolve around 12 stars. The final object is M71, a mag +8 globular cluster. For full details of where to find these objects and how best to see them, pick up the current issue of Sky at Night magazine NGC 6946 The Fireworks Galaxy – Astronomy Now’s object of the month is NGC 6946, a stunning face-on spiral galaxy on the border between Cetus and Cygnus. Its four spiral arms are blue but are dotted with pinkish coloured HII star forming regions, giving some stunning colour contrast. In the past 100 years there have been 10 supernova explosions with in this galaxy (the usual rate is around 1 per century!). Its overall brightness is affected by dust from the nearby Milky Way, but at mag +8.9 it should be visible through most telescopes. If you are imaging it with a small refractor, you should be able to capture the nearby open cluster NGC 6939 within the same field of view. If imaging with a larger aperture, make sure you capture lots of luminance images to help bring out the faint detail. A H-alpha narrowband filter will show up the details within the HII regions. For more information on how to observe, image or sketch this object, take a look at the current edition of Astronomy Now magazine Sky Tour – Astronomy Now’s Sky Tour this month takes you on a tour of the numerous planetary nebulae which are observable during the summer. There are 10 planetary nebulae to look for, all in the region of Cygnus, Vulpecula, Sagitta, Dephinus, Aquila and Sagittarius, including the Helix Nebula, Saturn Nebula, Little Gem and many more. For more information about these objects, take a look at the current edition of Astronomy Now magazine Solar Observations – although the days are shortening, there is still plenty of time for solar observing. A white light filter will show sunspots, faculae and maybe some granulation. A specialist hydrogen-alpha telescope will show filaments, prominences and if you are lucky you may catch a solar flare in action. Also, if there is a lot of high level cirrus cloud around, keep a look out for solar optical phenomena such as parhelia (sundogs), 22 degree haloes and the various arcs associated with ice haloes SAFETY WARNING: Never attempt to observe or photograph the Sun without the correct equipment. Failure to do so will result in permanent damage to your eyes or even blindness! International Space Station – There are ISS passes visible from the UK during the first 9 days of August, then it leaves our skies for a few weeks. For the exact timings of the passes from your location, visit www.heavens-above.com Don’t forget to check for Iridium flare times for your location there too. Mayak – keep your eyes out for the new Russian satellite, Mayak, which was launched during July 2017 with the sole purpose of being the brightest satellite in the sky. Once fully deployed, it will have very large reflective panels. When these catch sunlight, they may even reach mag -10 during visible passes, which will definitely rival the ISS! It is visible from the UK throughout the whole of August. For details of pass times, check www.heavens-above.com
Comets Visible This Month: Comet C/2015 ER61 (PanSTARRS) – This month, ER61 is much better placed for observation from the UK. Moving through Taurus, it rises in the NE at around midnight at the start of August (but by the end of the month it is rising at around 10:30pm) and reaches about 30 degrees above the eastern horizon by 3am. Between 10th – 27th August, there will be an excellent photo opportunity as the comet passes within half a degree of M45 The Pleiades. It is predicted that ER61 will still be around mag +10 during August.Click here to view the finder chart: http://bit.ly/2hcqz6O There are several other comets in the mag +11 to +15 range. Details of these can be found in the links below.
For up to date information about the fainter comets which are visible, please visit: https://in-the-sky.org/data/comets.php, the BAA Comets Section: https://www.ast.cam.ac.uk/~jds/ or Seiichi Yoshida’s home page: http://www.aerith.net/index.html
NB: All of the information in this sky guide is taken from Night Scenes 2017 by Paul L Money, Philips Stargazing 2017 by Heather Couper and Nigel Henbest, 2017 Yearbook of Astronomy by Richard Pearson and Brian Jones, Astronomy Now Magazine, Sky at Night Magazine, Stellarium, the BAA Comets Section website https://www.ast.cam.ac.uk/~jds/, www.inthesky.org and www.heavens-above.com Information collated by Mary McIntyre. For regular updates about the events happening in the sky this month, follow the Nightscenes Monthly Night Sky Facebook page at www.facebook.com/AstrospacePublications
Scientists observe the gravitational waves for the
second time
Written By Abdellah Akdad The discovery of gravitational waves predicted by Albert Einstein a hundred years ago in February was not mere assumptions after scientists said on Wednesday 15-06-2016 they had detected those waves for the second time. The researchers said they detected gravity waves after two black holes ran around each other and formed one larger hole 1.4 billion years ago. This ancient collision created waves in time and space or so-called "space-time", a fusion of the concepts of time and spa These waves, rippling across the Universe at the speed of light, were observed by two observatories in the United States late on 25 December 2015 (the early hours of the morning of 26 December). Monitoring devices are located in Livingston, Louisiana and Hanford, Washington The first wave monitoring event occurred in September and was announced on February 11. The discovery provoked a scientific sensation and became a marker in physics and astronomy and brought out Einstein's theory of gravity in 1916 to the world of application. The waves observed in September and December result in the fusion of two black holes, two areas so dense with matter that no light atom is allowed to penetrate. "We're starting to get a flash of new astronomical information that can only come from such gravitational wave detectors," said David Schumaker, a Massachusetts Institute of Technology researcher. The two black holes that created the newly observed waves were larger than the sun, one at eight times and one at 14 times before they merged and form a black hole that is 21 times larger than the sun. Scientists can use the time difference to form a rough idea of where fusion occurs between the holes. Scientists said that the second monitoring confirms that the proliferation of black holes in binary is relatively common.
Back page image courtesy of Abdellah Akdad