Astronomy

ASTRONEWS

FAST

FAC T

12 ASTRONOMY • DECEMBER 2015

A SLOW DEATH. A section of the cosmos produces just half the energy it did 2 billion years ago, according to the

multiwavelength Galaxy And Mass Assembly project, which surveyed 200,000 galaxies using many telescopes.

BRIEFCASE

DOUBLE BLACK HOLE

Astronomers found that Markarian 231, the closest gal-

axy to Earth that hosts a quasar — an actively feeding

black hole — actually sports twins. Research published

August 20 in The Astrophysical Journal shows that a

smaller black hole circles the supermassive central one,

carving out a doughnut hole around the galaxy’s core.

Since most galaxies contain central black holes and gal-

axy mergers are common, astronomers suspect that

binary black holes may be as well. Like their hosts, the

black holes should eventually merge.

• LADEE FINDS NEON
  NASA’s Lunar Atmosphere and Dust Environment
  Explorer (LADEE) spacecraft confirmed the presence of
  neon on the Moon, which has been suspected since the
  Apollo days, but only proven in a study published
  May 28 in Geophysical Research Letters. The Moon’s
  atmosphere is extremely thin — 100 trillion times less
  dense than the air we breathe on Earth. Most of it is
  thought to come from the solar wind, but LADEE also
  revealed that lunar rocks outgas argon and helium.


• 
  

  ETERNAL RING
  A new study published in the August 4 issue of the
  Proceedings of the National Academy of Sciences answers
  a long-standing question about the size of particles in
  Saturn’s rings. Researchers proved that the distribution
  of dust and pebbles is exactly what should occur in a
  system where collisions are common, so that small
  grains stick together and larger ones break apart at
  steady rates. — Korey Haynes

  
  

NASA

made its one and only visit to

Neptune more than a quarter-

century ago. And for years, planetary scien-

tists have bemoaned a predicted 50-year

gap between that Voyager 2 f lyby and any

follow-up mission.

Jim Green, NASA’s head of planetary

sciences, took a step toward narrowing that

gap in August at the Outer Planets

Assessment Group meeting in Laurel,

Maryland, by announcing that NASA will

study a potential f lagship mission to Uranus

and/or Neptune. If approved, it would be

the next big mission following Mars

and the Europa f lyby. Past f lagship missions

include Cassini, Galileo, and Voyager.

Neptune’s moon Triton is an enticing

option for many of the same reasons that

prompted the Europa mission.

Triton is nearly as big as Earth’s Moon

but has smoke-stack-like plumes from ice

volcanoes that erupt nitrogen frost onto its

surface. For its part, Uranus has five moons

big enough to be considered dwarf planets

if they orbited the Sun on their own.

Argo, the last proposed mission to

Neptune, was grounded because NASA

didn’t have enough plutonium to power all

of its spacecraft, according to one of its

designers. Candice Hansen of the Jet

Propulsion Laboratory says there was a

launch window from 2015 to 2020 that

would put Argo at Neptune in a decade via

gravity assists from Jupiter and Saturn.

That timeline is now impossible to meet.

But she says the Space Launch System

rocket that NASA is currently building

could eliminate the need for gravity assists

and allow a mission to get to Uranus or

Neptune much faster.

Another exciting potential mission

option announced in August is the

Enceladus Life Finder, or ELF, which

would orbit Saturn and sample the moon’s

curtain-like plumes of water that the

Cassini mission found streaming from its

icy surface. If approved, ELF would catch

the water and then directly sample it for

signs of life. — Eric Betz

NASA STUDIES TRIP TO AN ICE GIANT

Astronomers have traditionally associated the

most common type of meteorites, known as

H chondrites, with a main-belt asteroid called

6 Hebe. This asteroid orbits roughly three times

for every trip Jupiter takes around the Sun,

placing it in a resonance orbit, which makes it a

likely suspect to send accompanying rocky mis-

siles toward Earth.

However, spectral observations of a passing

asteroid called 2007 PA 8 , published in the

July 20 issue of The Astrophysical Journal, reveal

its remarkable similarities to H chondrites,

implying that some of these meteorites might

have originated with 2007 PA 8 ’s family farther

out in the main belt. — K. H.

Mundane meteorites

have unexpected origin

NEXT VOYAGER. In 1989, the Voyager 2 space-

craft became the first and last to see Neptune. NASA

WHERE IN THE BELT? Scientists used Earth-based

observatories to study a passing asteroid and then

compared it to meteorites that have plummeted to

Earth in the past. NASA/ESA/STSCI

SPACE STAMINA. Astronaut Scott Kelly is making headlines with his “Year in Space.” And when he returns in

March, Kelly will hold the record for the American with the most off-Earth time at 522 days. But that doesn’t even

crack the top 10 list of Russians in space. In July, cosmonaut Gennady Padalka, orbiting alongside Kelly, broke his

comrade Sergei Krikalev’s record of 803 days in orbit. ASTRONOMY: ERIC BETZ AND LUANN BELTER; NASA/BILL INGALLS (KELLY IMAGE)

HOW MANY YEARS

IN SPACE?

Of the roughly 46,600 total person

days spent in orbit, Russians have

logged more than 25,000 compared

to just over 17,700 for Americans.

TOTAL TIME IN SPACE

Gennady Padalka 878 DAYS*

Sergei Krikalev 803 DAYS

Aleksandr Kaleri 769 DAYS

Sergei Avdeyev 747 DAYS

Valeri Polyakov 678 DAYS

Anatoly Solovyev 651 DAYS

Yuri Malenchenko 641 DAYS

Viktor Afanasyev 555 DAYS

Yury Usachev 552 DAYS

Pavel Vinogradov 546 DAYS

Scott Kelly 522 DAYS*

*UPON COMPLETION