- 3892 - MASSIVE BLACK HOLES - went missing? This is a really surprising result. If expansionary dark energy does lurk inside the cores of black holes, it will solve two long-standing puzzles faced by Einstein’s general theory of relativity, which describes how gravity affects the universe at large scales.
----------- 3892 - MASSIVE BLACK HOLES - went missing?
-
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.
-
- Despite
searching with NASA's Chandra X-ray Observatory and Hubble Space Telescope,
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.
-
- 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 heft of some of the largest
known black holes in the Universe.
-
- Astronomers
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. Astronomers 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, 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 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.
-
- 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.
-
- Astronomers
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.
-
- They
concluded that either there is no black hole at any of these locations, or that
it is pulling material in too slowly to produce a detectable X-ray signal.
-
- The mystery
of this gigantic black hole's location therefore continues. 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.
-
-
Supermassive black holes could be the engines driving the expansion of
the universe, according to research that proposes a solution to "one of
the biggest problems in cosmology."
-
- By comparing supermassive black holes across
nine billion years of cosmic history, astronomers have discovered a clue that
the ravenous behemoths lurking at the hearts of most large galaxies may be the
source of dark energy, the mysterious force that makes up 68% of the known
universe and causes its accelerating expansion.
-
- Over the
last century, astronomers discovered that the universe was expanding at an ever
faster pace. This was surprising given that, acting on its own, gravity should
be expected to slowly crumple the cosmos together in an event known as the Big
Crunch.
-
- To explain
the discrepancy, scientists proposed that something powerful enough to
counteract gravity must exist, and was pushing everything in the universe further
apart. They named that something “dark energy”.
-
- But for
dark energy to reverse a cosmic collapse, it would have to be present in such
enormous quantities that it makes up the vast majority of the universe.
-
- Now, the new
studies have seemingly found a clue as to how the hidden phenomenon works.
Comparing the masses of black holes at the centers of two sets of
galaxies. The astronomers found that
throughout the universe giant black holes had ballooned to be seven to 20 times
larger than they once were, a monstrous growth that couldn't be explained
simply by black holes devouring stars or colliding and combining with each
other.
-
- The
researchers propose that black holes are growing in lockstep with the universe,
overcoming the star-crushing, light-capturing forces at their cores with a
hypothetical type of dark energy called vacuum energy that makes them expand
ever outwards. And, somehow, they drag the entire fabric of the cosmos out with
them.
-
- This is a
really surprising result. If expansionary dark energy does lurk inside the
cores of black holes, it will solve two long-standing puzzles faced by
Einstein’s general theory of relativity, which describes how gravity affects
the universe at large scales.
-
- Firstly, it
would explain how the universe doesn’t collapse due to the large and ubiquitous
force of gravitational attraction and, secondly, it would do away with the need
for singularities (infinitesimal points where the laws of physics break down)
to explain the workings of black holes' dark hearts.
-
- To confirm
their theory, astrophysicists will need to ensure that nothing else is
contributing to the black holes' mysterious growth by making even more detailed
observations of their masses throughout time, while also closely tracking the
increase to these masses with the expansion of the universe.
-
February
26, 2023 MASSIVE BLACK
HOLES - and universe expansion? 3892
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------ “Jim Detrick” -----------
---------------------
--- Sunday, February 26, 2023 ---------------------------
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