Astronomy - February 2014

M star

K star

G star

Mass of star (solar mass)

Average radius of orbit (astronomical unit)

Mercury Venus Earth Mars

HD 40307 g

Kepler-22b

Gliese 163 c

Kepler-61b

HD 85512 b

Kepler-62e Kepler-62f

Gliese 667C c

Gliese 581 d

Gliese 667C f Gliese 667C e

Kepler-69c

0.

0.

0.

0.

1

0.1 0.4 1.

Scientists still have a lot

of Kepler data to comb

through; it holds another

roughly three dozen possible

habitable-zone planets.

ASTRONEWS

FAST

FACT

WWW.ASTRONOMY.COM 19

TESTING, TESTING. NASA launched a sounding rocket October 21 to use when calibrating an ultraviolet instrument

aboard the Solar Dynamics Observatory. Its 173-mile-high (278 kilometers) flight took 15 minutes.

New shape to the coldest place in space

BRISK BOOMERANG.

Using the Atacama Large

Millimeter/submillimeter

Array (ALMA), astrono-

mers have revealed the

true shape of the coldest

known object in the

universe, the Boomerang

Nebula. This preplanetary

nebula, which represents

the stage before the

remnant star produces

enough ultraviolet

radiation to produce

a planetary nebula’s

characteristic glow, got

its name because it looks

like a double lobe with

a narrow waist in visible

light. ALMA, however, dis-

covered that the Boomer-

ang’s cold molecular gas

actually creates a more

elongated shape, shown

in red atop blue Hubble

Space Telescope data

in this image released

October 24. At –458°

Fahrenheit (–272° Cel-

sius), the nebula is colder

than the faint afterglow of

the Big Bang, the natural

background temperature

BILL SAXTON; NRAO/AUI/NSF; NASA/HUBBLE; RAGHVENDRA SAHAI of space. — K. F.

Planck mission over

On October 23, the Planck mission team sent the
final command to the telescope, marking the
end of operations. The spacecraft launched May
14, 2009, and observed the microwave sky for
nearly 4.5 years.
Planck had two detectors: the High Frequency
Instrument (HFI) studied shorter wavelengths
(higher energies and higher temperatures), and
the Low Frequency Instrument (LFI) observed lon-
ger wavelengths (which correspond to lower
energies and cooler temperatures). While the HFI
took its last data in January 2012, the LFI contin-
ued observing until October 3, 2013.
Scientists have used this data to uncover
thousands of cold objects — like clouds of gas
and dust that will form stars. But the project’s
main goal was to measure the tiny differences in
temperature across the sky — in what’s called
the cosmic microwave background (CMB). In
March 2013, the Planck team released its first
cosmology results, which incorporated 15.
months of observations. Part of that release
included a detailed map of the CMB’s tempera-
ture fluctuations, thus achieving the project’s
goal. According to the craft’s CMB measure-
ments, the universe is 13.8 billion years old and
contains 4.9 percent normal matter, 26.8 percent
dark matter (an invisible mass), and 68.3 percent
dark energy (the mysterious something that’s
speeding up the universe’s expansion).
Astronomers also teased out of the Planck
data the universe’s overall mass distribution.
While this map doesn’t show individual structures,
it does provide scientists with a general view of
how matter clusters together in the cosmos. The
distribution matches that expected for a universe
composed of about two-thirds dark energy.
The Planck team plans to release another set
of results later this year, which will incorporate
all observations collected. — L. K.

The chance that a supernova explosion will

occur in our galaxy in the next 50 years and

will be visible in infrared light, according to a

study published in the December 1 issue of

The Astrophysical Journal.

WHAT EXOPLANETS MIGHT BE HABITABLE?

EARTH TWINS? A star’s habitable zone (HZ) is the orbital region with the right temperature to allow liquid water on

a planet’s surface. Both Earth and, perhaps surprisingly, Mars sit within the Sun’s HZ. This diagram shows the poten-

tially habitable worlds so far discovered. The HZ edges are based on research from Ravi Kumar Kopparapu of Pennsyl-

vania State University and colleagues published in 2013 in The Astrophysical Journal. They ignored the effects of water

clouds in their model, which would push the inner boundaries nearer to their stars. ASTRONOMY: LIZ KRUESI AND ROEN KELLY

100%

MISSION OVER. The European Space Agency’s Planck
mission officially ended October 23. ESA