Astronomy

ASTRONEWS

20 ASTRONOMY • APRIL 2018

RZ Piscium is a puzzling star 550 light-years

away in the constellation Pisces. Astronomers

have known for some time that the star experi-

ences dramatic and erratic dimming episodes

lasting as long as two days.

During these episodes, the star drops down

to 10 times fainter than usual. Furthermore, it

produces much more infrared light than most

stars, implying it is surrounded by enormous

quantities of dust. This has led some astrono-

mers to conclude that RZ Piscium is a young,

Sun-like star surrounded by a dusty, planet-

forming disk.

However, the jury is split. Other astronomers

have suggested that RZ Piscium is a bit older

than the Sun, and it is beginning its transition

into a red giant. But if this is the case, the star’s

strong stellar winds would have already blown

away any dust remaining from its early youth,

meaning there would need to be another dust

source to explain the star’s infrared glow.

So is the star young or old? According to

a paper published December 21 in The

Astronomical Journal, RZ Piscium is neither.

Based on observations made using the XMM-

Newton satellite, the Shane 3-meter telescope

at Lick Observatory, and the 10-meter Keck I

Telescope in Hawaii, researchers determined

that RZ Piscium is too young to be entering the

red giant phase of its life, but too old to be sur-

rounded by a dusty, planet-forming disk.

According to the study, the best explanation

that fits all the data is that the star is shrouded

in dust and debris from the destruction of one

or more massive, gas-rich planets. “Most Sun-

like stars have lost their planet-forming disks

within a few million years of their birth,” said

co-author Ben Zuckerman in a press release.

“The fact that RZ Piscium hosts so much gas

and dust after tens of millions of years means

it’s probably destroying, rather than building,

planets.” — J.P.

Mysterious ‘winking’

star could be

devouring planets

Dark matter explains galaxy cluster observations

Enormous bubbles cover

surface of red giant star

The Sun’s surface is speckled with roughly

2 million convective cells, each about 1,

miles (1,600 kilometers) across. Though the

Sun’s pockmarks have been well-studied

over the years, astronomers had never before

observed the convective cells of another star.

In a study published December 20 in Nature,

an international team of astronomers revealed

that the surface of Pi^1 Gruis contains only a few

convective cells. These cells are enormous,

each spanning around 75 million miles

(120 million km), about a quarter of the red

giant’s diameter. Located about 530 light-years

away in the constellation Grus the Crane,

Pi^1 Gruis is about the same mass as the Sun,

yet its radius is 700 times as large. It also shines

several thousand times brighter than the Sun.

While this may be the first surface of another

star we have ever observed in such detail, it

certainly will not be the last. — J.P.

LIGHT FROM DARK. Supermassive black holes not only establish themselves well before a galaxy forms around them,

but they also have strong winds that blow out through the entire galaxy, impacting the development of stars.

STAY BACK. This artist’s concept shows RZ Piscium, a star about 550 light-years away, which undergoes

erratic dips in brightness that make it appear 10 times fainter than usual. One proposed theory to explain

these dips is that a giant planet near the star is slowly disintegrating. As it does, clouds of gas and dust

from the dissolving planet block light from the star. NASA’S GODDARD SPACE FLIGHT CENTER/CI LAB

X-RAY: NASA/CXO/OXFORD UNIVERSITY/J. CONLON ET AL. RADIO: NRAO/AUI/NSF/UNIV. OF MONTREAL/GENDRON-MARSOLAIS ET AL. OPTICAL: NASA

/ESA/IOA/A. F

ABIAN ET AL.; DSS

MANY COLORS. By combining many wavelengths of light into a single image, astronomers can better

understand the many processes at work throughout the universe — including the influence of unseen

dark matter. This image of the Perseus galaxy cluster includes X-ray data (in blue) from the Chandra X-ray

Observatory, optical data (in pink) from the Hubble Space Telescope, and radio data (in red) from the Very

Large Array. In 2014, observers noted an increase in X-rays at an energy of 3.5 kiloelectron volts from the

hot gas in the center of the cluster. Further observations show that X-rays of this same energy are being

absorbed near the supermassive black hole at the center of the cluster. One possible culprit is fluorescent

dark matter, a theorized type of dark matter particle capable of interacting with and absorbing these X-rays

near the black hole and then re-emitting them in all directions. — A.K.

BOIL AND

BUBBLE.

The surface of Pi^1

Gruis was imaged

by ESO’s Very

Large Telescope,

showing a level of

detail never before

achieved on a star

other than the

Sun. ESO