Astronomy

ASTRONEWS

FAST

FAC T

Polaris, currently 0.77° from

the North Celestial Pole, will

be closest to that point in 2102,

when it will lie 0.46° away.

Thuban

22300 to 24100

Vega

13100 to

15000

North

Celestial Pole

2017

to 8000

Polaris

500 to 3000

Alrai

Iota 3000 to 5200

5200 to 6800

Alderamin

6800 to 8000

Deneb

9600 to

10300

Delta

11000 to

12000

Ta u

18500 to 21700 Edasich

21700 to 22300 Kochab24100 to 26500

0

5000

10000

15000

20000

CYGNUS CEPHEUS

LY R A

HERCULES

BIG

DIPPER

URSA

MINOR

DRACO

12 ASTRONOMY • JANUARY 2018

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.

BRIEFCASE

NEIGHBORHOOD WATCH

Coryn Bailer-Jones of the Max

Planck Institute for Astronomy

has published the first system-

atic estimate of how often

other stars wander into our

solar neighborhood. Using

data from the European Space

Agency satellite Gaia, Bailer-

Jones found that every million

years, between 490 and 600

stars typically pass within

5 parsecs (16.3 light-years) of

the Sun. Astronomers are inter-

ested 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.

• TURBULENCE AHEAD
  Researchers once thought
  Jupiter’s aurorae were created
  the same way as Earth’s, where
  energetic particles are acceler-
  ated by differences in strength
  between atmospheric mag-
  netic fields, called electric
  potentials. But the strongest
  aurorae on Jupiter are not
  always associated with the big-
  gest electric potentials, as on
  Earth. Instead, it appears a dif-
  ferent cause is responsible for
  the most powerful displays. “At
  Jupiter, the brightest aurorae
  are caused by some kind of tur-
  bulent 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.


• 
  

  MIDDLE GROUND
  In a paper published
  September 4 in Nature
  Astronomy, a team of astrono-
  mers led by Tomoharu Oka of
  Keio University in Yokohama,
  Japan, shows evidence that a
  gas cloud called CO-0.40-0.
  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 supermas-
  sive black hole, Sagittarius A*,
  though 500 times fainter, sug-
  gesting a black hole a few hun-
  dred times smaller. — J.P.,
  John Wenz, Alison Klesman

  
  

F

rom prompting star forma-

tion to driving accretion

around supermassive black

holes, magnetic fields

inf luence nearly every astro-

physical process. However, one

of the biggest hurdles in study-

ing 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 light-

years 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, pro-

viding new insight into how these fields have

evolved in the universe over cosmic timescales.

The scientists investigated the galaxy using a phe-

nomenon 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.

YOUNG GALAXIES MAY HAVE OLD MAGNETIC FIELDS

The light passing through

the galaxy’s edges is further

affected by any local mag-

netic fields, which can

change the light’s polariza-

tion, 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 deter-

mined 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

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

ASTRONOMY

: ROEN KELLY

FUTURE

NORTH STARS

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

Foreground

galaxy

Lensed images of

CLASS B1152+