Astronomy - USA (2022-06)

Supermassive

black hole

Accretion

disk

Gas clouds

Narrow

line

region

Broad

line

region

Jet

Dusty torus

Corona

of gas

Singularity

Event

horizon

Supermassive

black hole

Accretion

disk

Corona

of gas

Singularity

Event

horizon

Proxima d was found using the radial velocity method, where astronomers monitor a

star’s light for subtle changes in wavelength that occur as the gravity of an orbiting planet

tugs on it. This is the same method used to detect Proxima Centauri’s other two planets,

Proxima b and c. But Proxima d’s detection is impressive because, as it is so light, its

effect on its host star was small. By contrast, Proxima b and c are more massive and were

thus easier to find — Proxima b is roughly the same mass as Earth and Proxima c is a

super-Earth about six times our planet’s mass.

In fact, Proxima d is the lightest exoplanet discovered to date using the radial veloc-

ity method. The team found it with a new instrument called the Echelle SPectrograph

for Rocky Exoplanets and Stable Spectroscopic Observations, or ESPRESSO, on the

European Southern Observatory’s Very Large Telescope in Chile.

Now that ESPRESSO has shown its mettle at spotting small planets, astronomers are

hoping it will uncover many more terrestrial worlds, perhaps much like our own, in more

distant systems. — A.K.

supermassive black hole surrounded by a

torus, or doughnut-shaped ring, of dust.

The different AGN classes are the result of

the angle from which we see the system.

M77 is a type 2 AGN that astronomers

have long suspected is embedded in a

thick buffer of dust. Images have previ-

ously spotted warm dust near the galaxy’s

center. But recent observations suggest

that the ring of dust around the black

hole was too thin and not oriented at

the precise angle to hide the black hole

as expected, challenging rather than

supporting the unified model.

A CLEARER PICTURE

Researchers needed a better picture of the

dust to be sure. So, they zeroed in on the

galaxy’s center with the Multi AperTure

mid-Infrared SpectroScopic Experiment

(MATISSE). They employed a technique

called interferometry, which dramati-

cally boosts the amount of detail visible.

When combined with radio data from the

Atacama Large Millimeter/submillimeter

Array and the National Radio Astronomy

Observatory’s Very Long Baseline Array,

the team could finally map out M77’s cen-

tral dust. They found that the black hole

is completely embedded in the thicker,

ring-shaped center of a larger, edge-on

disk of dust, confirming what is expected

from the unified model.

Now the trick is to determine whether

M77’s black hole is indeed typical and if

the unified model accurately predicts what

we see in other galaxies. The team plans

to observe other AGN with MATISSE to

find whether they, too, match expecta-

tions. And confirming the unified model

will also boost our understanding how

black hole’s host galaxies form, grow, and

ultimately die.— ALISON KLESMAN

MOON BUGGY

Toyota is partnering with the

Japan Aerospace Exploration

Agency to develop a pressurized,

crew-carrying rover called the

Lunar Cruiser, slated for launch

by the end of the decade.

PLANETARY

METAMORPHOSIS

Astronomers have spotted two

mini-Neptune exoplanets being

stripped of their puffy

atmospheres by radiation from

their host stars. This process

could ultimately transform the

worlds into smaller super-Earths.

PRIMEVAL MASHUP

The Milky Way likely underwent a

sixth, previously unknown galaxy

merger some 8 billion to 10 billion

years ago. Evidence comes from

a group of stars that were once

part of the cannibalized satellite,

Pontus, and now reside in the

outer halo of our galaxy.

TWICE THE TROJANS

Our family of Trojans — asteroids

that lead or trail Earth in its orbit

— just doubled in size, from one

to two. But astronomers predict

newly added asteroid 2020 XL 5

will only be considered a Trojan

for roughly another 4,000 years.

WRECKED WORLD

Sixty-five Moon-sized debris

clouds have been found around

WD1054-226, a white dwarf some

115 light-years away. Because the

dusty, irregularly shaped clouds

are evenly spaced, astronomers

think an intact planet in the star’s

habitable zone might be

shepherding them.

AMBITIOUS AGENDA

According to a white paper, China

aims to send a sample-collecting

spacecraft to a near-Earth

asteroid, build a space telescope

that rivals Hubble, and launch

two more Chang’e lunar missions

to survey and sample the Moon’s

south polar region. — JAKE PARKS

QUICK

TAKE S

WWW.ASTRONOMY.COM 9

CHANGING PERSPECTIVES. The unified model
of AGN states that all AGN are essentially the
same, simply viewed at different angles. Every
one contains a supermassive black hole, an
accretion disk, a fast-moving gas region, an
obscuring torus of dust, and a slower-moving
gas region. Some AGN also have powerful jets.
ASTRONOMY: ROEN KELLY