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Black holesRate of star formationWWW.ASTRONOMY.COM 11
HOW SUPERMASSIVE
BLACK HOLES KILL
THEIR GALAXIES
GALACTIC HEARTWORM. Eventually
star formation in galaxies turns off,
but astronomers don’t understand
precisely what causes this quench-
ing. One of the leading ideas is that
the galaxy’s central black hole acts
like a parasite. As the supermassive
black hole (SMBH) feeds on nearby
material, it disrupts the galaxy’s gas
supply, cutting off available gas for
new stars. New research indicates
that quenching depends on the mass
of both the central black hole and of the stars in the galaxy combined with
the galaxy’s radius. Smaller galaxies more densely packed with stars tend to
have larger SMBHs, meaning their star formation is cut off a lot sooner than
it is for galaxies whose stars are more spread out, as seen in the illustration.
Larger, more diffuse galaxies, however, must evolve further before their
SMBHs are massive enough to affect their star formation. — CAITLYN BUONGIORNOAmateur astronomers have always been
on the front lines of planetary defense,
discovering and tracking near-Earth
asteroids (NEAs) that could one day
collide with our planet. But now they’ve
taken on a new role: helping to map such
an object, revealing its shape.
In a project led by researchers at
the SETI Institute, 26 backyard observ-
ers from seven countries targeted the
1.2-mile-wide (2 kilometers) asteroid 1999
AP 10. All of the observers used an eVscope
— a new “smart” telescope model with a
built-in CMOS detector produced by the
startup Unistellar. (Read our review of the
eVscope on page 58 of the March issue.)
Their analysis exploited changes inthe asteroid’s brightness as it tumbled
through space, reflecting sunlight differ-
ently at every angle. Through October
and November 2020, eVscope users col-
lected 81 sets of observations, which the
researchers used (along with some archi-
val data from 2009) to reverse engineer
the asteroid’s physical shape.
The team presented their results
December 9 at the fall meeting of the
American Geophysical Union, held online.
Franck Marchis of the SETI Institute
tells Astronomy that a network of
thousands of identical eVscopes is a“game-changer” for pro-am teams. The
eVscope calibrates and processes its
observations automatically, and results
from standardized equipment can be
combined more consistently, he notes.
The field of planetary defense suffered
a major loss when Arecibo Observatory
collapsed in December — it obtained
high-resolution data of 20 to 30 NEAs per
year. Marchis hopes eVscope campaigns
will map one or two NEAs annually, and
though that’s a small fraction of Arecibo’s
former output, he says it could help “fill
up the gap left by Arecibo.” — M.Z.Citizen
astronomers
map near-Earth
asteroid
The Milky Way’s sister galaxy
Andromeda is more quenched than
our own and has a supermassive
black hole 50 times the mass of the
Milky Way’s central black hole.FAST FACT
JO
SEF^ HANUŠ,^ CHARLESUNIVERSITY&
FRANCKMARCHI
S,^
SETI^
IN
ST
ITUTEMODEL POSES. This model of the near-Earth asteroid 1999 AP 10
was compiled using observations from citizen astronomers.ASTR
ONOMY:^
ROENK
EL
LY,SANDRAFABER/
SOFIAQ
UI
ROS/
SDSS