- 3875
- MASSIVE BLACKHOLE
- not detected? The James Webb Space Telescope may be able
to reveal the presence of a supermassive black hole in the center of the galaxy
or one of the clumps of stars. If Webb is unable to find the black hole, then
the best explanation is that the black hole has recoiled well out of the center
of the galaxy.
-
--------------- 3875 - MASSIVE BLACKHOLE - not detected
- Astronomers
are searching for signs of a supermassive black hole in the galaxy cluster
Abell 2261. Nearly all large galaxies
contain central black holes, and the galaxy in the middle of Abell 2261 is
expected to contain a particularly massive one.
-
- Scientists
think this galaxy underwent a merger with another galaxy in the past, which
could have caused a newly formed larger black hole to be ejected. Despite careful searches with Chandra and
other telescopes, astronomers do not yet know what happened to this giant black
hole.
-
- Astronomers
have no evidence that a distant black hole estimated to weigh between 3 billion
and 100 billion times the mass of the Sun is anywhere to be found.
-
- This
missing black hole should be in the enormous galaxy in the center of the galaxy
cluster Abell 2261, which is located about 2.7 billion light years from Earth.
The composite image of Abell 2261 contains optical data from Hubble and the
Subaru Telescope showing galaxies in the cluster and in the background, and
Chandra X-ray data showing hot gas pervading the cluster.
-
- Nearly every large galaxy in the Universe
contains a supermassive black hole in their center, with a mass that is
millions or billions of times that of the Sun. Since the mass of a central
black hole usually tracks with the mass of the galaxy itself, astronomers
expect the galaxy in the center of Abell 2261 to contain a supermassive black
hole that rivals the mass of some of the largest known black holes in the
Universe.
-
- Using
Chandra data obtained in 1999 and 2004 astronomers had already searched the
center of Abell 2261's large central galaxy for signs of a supermassive black
hole. They looked for material that has been superheated as it fell towards the
black hole and produced X-rays, but did not detect such a source.
-
- Now, with
new, longer Chandra observations obtained in 2018, a team conducted a deeper
search for the black hole in the center of the galaxy. They also considered an
alternative explanation, in which the black hole was ejected from the host
galaxy's center.
-
- This violent
event may have resulted from two galaxies merging to form the observed galaxy,
accompanied by the central black hole in each galaxy merging to form one
enormous black hole.
-
- When black
holes merge, they produce ripples in spacetime called “gravitational waves”. If
the huge amount of gravitational waves generated by such an event were stronger
in one direction than another, the theory predicts that the new, even more
massive black hole would have been sent careening away from the center of the galaxy
in the opposite direction. This is called a “recoiling black hole”.
-
- Astronomers
have not found definitive evidence for recoiling black holes and it is not
known whether supermassive black holes even get close enough to each other to
produce gravitational waves and merge; so far, astronomers have only verified
the mergers of much smaller black holes.
-
- The
detection of recoiling supermassive black holes would embolden scientists using
and developing observatories to look for gravitational waves from merging
supermassive black holes.
-
- The galaxy
at the center of Abell 2261 is an excellent cluster to search for a recoiling
black hole because there are two indirect signs that a merger between two
massive black holes might have taken place.
-
- First,
data from the Hubble and Subaru optical observations reveal a galactic core,
the central region where the number of stars in the galaxy in a given patch of
the galaxy is at or close to the maximum value, that is much larger than
expected for a galaxy of its size.
-
- The second
sign is that the densest concentration of stars in the galaxy is over 2,000
light years away from the center of the galaxy, which is strikingly distant.
-
- During a
merger, the supermassive black hole in each galaxy sinks toward the center of
the newly coalesced galaxy. If they become bound to each other by gravity and
their orbit begins to shrink, the black holes are expected to interact with
surrounding stars and eject them from the center of the galaxy.
-
- This would
explain Abell 2261's large core. The off-center concentration of stars may also
have been caused by a violent event such as the merger of two supermassive
black holes and subsequent recoil of single, larger black hole that results.
-
- Even though
there are clues that a black hole merger took place, neither Chandra nor Hubble
data showed evidence for the black hole itself.
Astronomers look for a clump of
stars that might have been carried off by a recoiling black hole. They studied
three clumps near the center of the galaxy, and examined whether the motions of
stars in these clumps are high enough to suggest they contain a ten billion
solar mass black hole. No clear evidence for a black hole was found in two of
the clumps and the stars in the other one were too faint to produce useful
conclusions.
-
- Radio
emission detected near the center of the galaxy showed evidence that
supermassive black hole activity had occurred there 50 million years ago, but
does not indicate that the center of the galaxy currently contains such a black
hole.
-
- Astronomers
then turned to Chandra to look for material that had been superheated and
produced X-rays as it fell towards the black hole. While the Chandra data did
reveal that the densest hot gas was not in the center of the galaxy, they did
not reveal any possible X-ray signatures of a growing supermassive black hole —
no X-ray source was found in the center of the cluster, or in any of the clumps
of stars, or at the site of the radio emission.
-
February 13, 2023 MASSIVE BLACKHOLE
- not detected? 3868
----------------------------------------------------------------------------------------
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------ “Jim Detrick” -----------
---------------------
--- Wednesday, February 15, 2023 ---------------------------
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