ASTRONEWS
CHIMING IN. The new Canadian Hydrogen Intensity Mapping Experiment (CHIME) will probe nearly the entire observable universe in 3-D while studying dark energy and gravitational waves.
YOUNG GALAXIES MAY HAVE OLD MAGNETIC FIELDS
F
rom prompting star formation to driving accretion Lensed images of CLASS B1152+199 around supermassive black holes, magnetic fields influence nearly every astrophysical process. However, one of the biggest hurdles in studying the magnetic fields that pervade galaxies is their lack of strength. Millions of times weaker than Earth’s magnetic field, galactic magnetic fields are difficult to measure at great distances. But in an August 28 paper in Nature Astronomy, a team of researchers reported the best measurements yet of a magnetic field in a galaxy located a record-breaking 4.6 billion lightyears away. The team, led by Sui Ann Mao of the Max Planck Institute for Radio Astronomy, detected a magnetic field similar to the Milky Way’s in a host nearly 5 billion years younger, providing new insight into how these fields have evolved in the universe over cosmic timescales. The scientists investigated the galaxy using a phenomenon called gravitational lensing, which occurs when a massive object — the galaxy in this study — lines up between Earth and a distant object — in this case, a quasar (CLASS B1152+199). As divergent light rays from the quasar pass by the intervening galaxy, the galaxy’s gravity bends their path. to 8000
MAGNETIC FINGERPRINTS. The Hubble Space Telescope captured two gravitationally lensed images of a distant quasar behind a young foreground galaxy. The two images are light that has traveled through opposite ends of the galaxy, picking up information about its magnetic field along the way. MAO ET AL., NASA
The light passing through the galaxy’s edges is further affected by any local magnetic fields, which can change the light’s polarization, or the direction of its vibration. This effect is called Faraday rotation, and the stronger the magnetic field, the more the light’s polarization is rotated. By measuring this rotation in the light received from the background quasar, the researchers determined the young galaxy’s magnetic field is similar in size and strength to those found in the Milky Way and other nearby, older galaxies. One of the leading theories on the evolution of galactic magnetic fields is that they begin scrawny and tangled, then strengthen and organize over time. But that doesn’t seem to be the case here. “By catching magnetic fields when they’re so young, we can rule out some of the theories of where they come from,” Ellen Zweibel, a co-author on the study, said in a press release. — Jake Parks Foreground galaxy
Deneb CYG N US
FUTURE NORTH STARS
9600 to 10300
CEPHEUS 10000
Delta
11000 to 12000
5000
Alderamin 6800 to 8000
LY R A
Alrai
Iota
3000 to 5200
5200 to 6800
Vega
13100 to 15000
Polaris
URSA M I NOR
DR AC O
500 to 3000 North Celestial Pole 2017
15000
0
Tau
18500 to 21700
HERCUL ES
Edasich
Kochab
21700 to 22300
24100 to 26500
Thuban ASTRONOMY: ROEN KELLY
20000
12
22300 to 24100
BIG DIPPER
A ST R O N O M Y • JA N UARY 2018
POLAR EXPRESS. Because of gravitational influences from the Sun and Moon, our planet wobbles like a top with a period of 25,772 years. That means the point above the North Pole (the North Celestial Pole, or NCP) traces a circle in that span. Currently, the closest bright star to the NCP is Polaris, the brightest star in the constellation Ursa Minor the Bear Cub. But 10 other relatively bright stars will lie closer to the NCP before Polaris once again assumes the mantle of North Star. — Michael E. Bakich
FAST FACT Polaris, currently 0.77° from the North Celestial Pole, will be closest to that point in 2102, when it will lie 0.46° away.
BRIEFCASE NEIGHBORHOOD WATCH Coryn Bailer-Jones of the Max Planck Institute for Astronomy has published the first systematic estimate of how often other stars wander into our solar neighborhood. Using data from the European Space Agency satellite Gaia, BailerJones found that every million years, between 490 and 600 stars typically pass within 5 parsecs (16.3 light-years) of the Sun. Astronomers are interested in these close stellar encounters because they can nudge comets out of the Oort Cloud and into the inner solar system, potentially wreaking havoc on unsuspecting planets like Earth.
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TURBULENCE AHEAD Researchers once thought Jupiter’s aurorae were created the same way as Earth’s, where energetic particles are accelerated by differences in strength between atmospheric magnetic fields, called electric potentials. But the strongest aurorae on Jupiter are not always associated with the biggest electric potentials, as on Earth. Instead, it appears a different cause is responsible for the most powerful displays. “At Jupiter, the brightest aurorae are caused by some kind of turbulent acceleration process that we do not understand very well,” Johns Hopkins University Applied Physics Laboratory researcher Barry Mauk said in a press release. At high energies, he said, “a new acceleration process takes over,” which Juno scientists are now working to understand.
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MIDDLE GROUND In a paper published September 4 in Nature Astronomy, a team of astronomers led by Tomoharu Oka of Keio University in Yokohama, Japan, shows evidence that a gas cloud called CO-0.40-0.22 near our galaxy’s center may harbor an intermediate-mass black hole. Gas particles inside CO-0.40-0.22 have motions consistent with an object 100,000 times the Sun’s mass. Radio emission measured from the cloud also bears striking similarities to the radio source associated with our galaxy’s 4 million-solar-mass supermassive black hole, Sagittarius A*, though 500 times fainter, suggesting a black hole a few hundred times smaller. — J.P., John Wenz, Alison Klesman