ASTRONEWS
WWW.ASTRONOMY.COM 13The Perseus cluster is experiencing giant waves of gas
Cygnus A is an elliptical galaxy nearly
800 million light-years away. Its cen-
ter hosts a supermassive black hole
at least 1 billion times the mass of
our Sun, but this well-known galaxy
also contains a surprise: a second
supermassive black hole, destined to
merge with the first.
Upgrades to the National Science
Foundation’s Jansky Very Large Array
(VLA) radio telescope in 2012
prompted observers to return to this
famous galaxy in 2015. Cygnus A had
not been observed in radio wave-
lengths since 1996. “To our surprise,
we found a prominent new feature
near the galaxy’s nucleus that did not
appear in any previously published
images,” Rick Perley of the National
Radio Astronomy Observatory
(NRAO) said in a press release. “Thisnew feature is bright enough that we
definitely would have seen it in the
earlier images if nothing had
changed. That means it must have
turned on sometime between 1996
and now.”
The astronomers who made the
discovery include Perley and his son,
Daniel Perley of the Astrophysics
Research Institute at Liverpool John
Moores University in the U.K., as well
as NRAO researchers Vivek Dhawan
and Chris Carilli. The results will be
published in The Astrophysical
Journal.
The object lies within 1,500 light-
years of the galaxy’s other supermas-
sive black hole. Astronomers
originally thought its emission repre-
sented a dense group of stars, based
on infrared images. But the fact thatthe object has grown brighter in
radio wavelengths has prompted
new consideration.
Now, “we think we’ve found a sec-
ond supermassive black hole in this
galaxy, indicating that it has merged
with another galaxy in the astronomi-
cally recent past,” said Carilli. “These
two would be one of the closest pairs
of supermassive black holes ever dis-
covered, likely themselves to merge
in the future.”
Although previously quiescent,
the second supermassive black hole
may have turned on after encounter-
ing a new source of fuel, likely stars
and dust in the galaxy. Now that it’s
visible, Daniel Perley said, “This new
object may have much to tell us
about the history of this galaxy.”
— A. K.QUICK TAKES
SHINE ON
Caltech chemical engineer
Konstantinos Giapis discovered
that comets make molecular
oxygen when surface ices are
sublimated by sunlight.(^) •
THE ELDER ONES
A Neptune-sized planet called
HAT-P-26b seems to have
retained its primordial
atmosphere. It has an
atmosphere and density
much like Saturn’s.
(^) •
ON THE RUN
NASA researchers discovered a
1 billion-solar-mass black hole
being kicked out of its galaxy
after two black holes merged.
(^) •
CONNECT THE DOTS
Astronomers discovered a
faint “bridge” magnetic field
between the Milky Way and
two of its satellite galaxies,
the Small and Large
Magellanic Clouds.
- BUCKETS OF RAIN
Early Mars may have had rain
strong enough to permanently
change the planet’s surface,
according to research
published in Icarus.
PUFFED UP
The planet KELT-11b has the
density of Styrofoam because
of the heat from its home star,
researchers at Lehigh
University discovered.
BLOW UP
Amateurs on Zooniverse.org
discovered a 960 million-year-
old supernova event named
SN 2017dxh.
EARLIER LAUNCH
The launch for NASA’s Psyche
mission has been moved up to
2022 to allow a faster trip to
the protoplanet core.
-^
BUT WITH A WHIMPER
The giant star N6946-BH
seemed to begin going super-
nova before it disappeared
instead, likely collapsing
directly into a black hole.
(^) •
TRICKSTER GOD
A transit of Europa across Io
helped astronomers identify
lava movements in Loki Patera,
the largest volcanic crater on
the latter moon. — John Wenz
IN PLAIN SIGHT. JPL researchers modeled galaxy mergers and found that the gas resulting from two black holes
merging may become obscured by dust kicked up during this process.
Second black hole spotted in famous galaxy
NASA/CXC/GSFC/S. A.
WALKER, ET AL.
TWO FOR ONE.
Cygnus A’s previously
identified central
supermassive black
hole appears in these
composite radio
(orange) and optical
(blue) images as a
large, bright, circular
source. The image
on the left is from
1989; the image on
the right was taken
in 2015. A new bright
radio source has
appeared since 1989;
astronomers believe
this second source is
also a supermassive
black hole. PERLEY ET AL.,
NRAO/AUI/NSF, NASA
STIRRED UP. Scientists found a wave of
incredibly hot gas in the Perseus galaxy
cluster, more than 200 million light-years
away. The wave is about 200,000 light-years
across, which is twice the size of the Milky
Way. The study, which was published in
the June issue of Monthly Notices of the
Royal Astronomical Society, used 10.4 days’
worth of high-resolution data and 8.5 days’
worth of wide-field observations from
NASA’s Chandra X-ray Observatory to cre-
ate an X-ray image of the rolling gas cloud.
Scientists estimate that it took 2.5 billion
years for the gas in the center of the Perseus
cluster, which burns at about 54 million
degrees F (30 million degrees C), to expand
a distance of 500,000 light-years. As the
smaller galaxy cluster flies by, it disrupts the
gas and causes rolling waves. The research-
ers say this wave is a much bigger version of
a Kelvin-Helmholtz wave, which is caused
by two fluids moving at different speeds
past each other. A simple earthly example
of this type of behavior is wind causing rip-
pling waves across bodies of water. — N. K.