Astronomy

ASTRONEWS

18 ASTRONOMY • JANUARY 2018

Research into the exoplanet

WASP-19b, classified as a hot Jupiter

because of its size and proximity

to its star, revealed something star-

tling: It has titanium oxide scattered

throughout its upper atmosphere.

Astronomers studied WASP-19b’s

atmosphere, which is measured at

3,600 degrees Fahrenheit (2,

degrees Celsius), using the FORS

instrument on the European Southern

Observatory’s Very Large Telescope.

As the planet passed in front of its

star, background light filtered

through its atmosphere, highlighting

some of the molecules and elements

present. FORS2 is a spectrograph,

which splits light into its constituent

parts to identify the signatures of ele-

ments and molecules. Using this tech-

nique, researchers found titanium

oxide, water, and sodium.

Previously, titanium oxide was

largely associated with cool stars. But

as we learn more about exoplanet

atmospheres, we are discovering

compounds like titanium oxide

are also found there. In this case,

titanium oxide may act as a heat

absorber, creating a thermal blanket

around the planet that traps heat

mostly in the upper atmosphere and

keeps lower areas cool.

The research, published

September 13 in Nature, highlights

Hot Jupiter’s skies contain titanium oxide

The prevailing theory in galactic

evolution is that massive elliptical

galaxies are formed when smaller

disk galaxies collide and merge.

However, an international team

of astronomers led by Ken-ichi

Tadaki of the National Astronomical

Observatory of Japan (NAOJ)

recently found that this is not

always the case.

“Massive elliptical galaxies are

believed to be formed from colli-

sions of disk galaxies,” said Tadaki in

a press release. “But, it is uncertain

whether all the elliptical galaxies

have experienced galaxy collision.

There may be an alternative path.”

Tadaki and his team discovered

that possible path. They found that

intense bursts of star formation can

swell disk-shaped galaxies — much

like yeast helps bread rise — morph-

ing them into ellipticals without the

help of collisions. The researchers

used the Hubble Space Telescope

and the Atacama Large Millimeter/

submillimeter Array to investigate 25

galaxies about 11 billion light-years

away, observing them just 3 billion

years after the Big Bang, at a time

when most galaxies were in their

infancy. They looked at both the

number of stars already shining and

the amount of gas and dust available

to form more stars. The team saw a

huge available reservoir of gas and

dust in the centers of these galaxies,

indicating that over time, star forma-

tion in the core will dominate the

galaxy’s appearance — “puffing up”

these galaxies and turning them into

ellipticals from within. — J.P.

Birthing stars makes galaxies swell

WORKING BACKWARD. Australian National University scientists created the best estimate of Earth’s composition,

which can now be used to improve solar system formation models.

LUNAR VIEWPOINT. During the August 21 total solar eclipse, NASA’s

Lunar Reconnaissance Orbiter (LRO) took an image of the eclipse as seen

from the Moon. LRO completed a slow 180° turn shortly after passing over

the Moon’s south pole, allowing it to look back toward Earth and snap a

photo as the shadow sped just north of Nashville, Tennessee, moving at

1,500 mph (670 m/s). LRO’s Narrow Angle Camera, which is actually two

high-resolution cameras, began imaging Earth at 2:25 P. M. EDT and took 18

seconds to complete the image, building it up line by line. The final picture

shows the eclipse near the longest duration of totality. — N.K.

What did totality look like

from the Moon?

our slowly increasing under-

standing of exoplanet atmo-

spheres, as we often find that

they’re vastly different from

those of our solar system’s plan-

ets. So far, all the information

we’ve gathered has been on

larger, hotter worlds, but

upcoming instruments may be

able to finally study Earth-sized

planets in distant solar systems

enough to detect a holy grail:

water vapor on worlds with

Earth-like temperatures. — J.W.

REVERSE THINKING. Astronomers think the titanium oxide in the hot Jupiter WASP-19b’s atmosphere leads to a situation

called temperature inversion: The upper atmosphere is hot, with cooler temperatures deeper down. ESO/M. KORNMESSER

RISE AND SHINE. Infrared light from the Hubble Space Telescope (right) emphasizes

the large galactic disk of a young galaxy. Optical light (middle) highlights three young

star clusters packed full of freshly formed stars near its center. Submillimeter waves from

the Atacama Large Millimeter/submillimeter Array (left) show a dense, star-forming cloud

of material in the galactic core. ALMA (ESO/NAOJ/NRAO), NASA/ESA HUBBLE SPACE TELESCOPE, TADAKI ET AL.

NASA/GSFC/ARIZONA STATE UNIVERSITY