- 4135 - BLACK HOLES
- many more found? - What has the new James Webb Space Telescope
(JWST) was discovering about black holes in one of its surveys of the
Universe? Six distant galaxies
captured by JWST are wowing astronomers.
It’s truly studying parts of the Universe that just weren’t available to
us technologically.
-------------- 4135 - BLACK HOLES - many more found?
- These
discoveries could help scientists to answer many long-standing queries about
black holes, such as how they managed to form early in the history of the
Universe and grow quickly into cosmic vacuums, sucking up everything around
them.
-
- Black holes
come in several sizes, but the ones JWST has been detecting are massive ones
that weigh millions to billions times as much as the Sun. We aren’t sure how
these black holes form, but it might involve massive stars or gas clouds
collapsing and then beginning to draw in nearby gas and dust. In this scenario,
these black-hole ‘seeds’ would grow rapidly, until they become gravitational
maws that lurk at the heart of most galaxies.
-
- Black holes
are not themselves visible, their immense gravitational pull means that not
even light can escape from them, but they can be spotted by searching for the
superheated gas that spirals around them like water going down a drain.
-
- Before
JWST, astronomers studied black holes using a range of space- and ground-based
telescopes. But these could spot only the brightest black holes, including
those that are relatively close to Earth.
JWST is designed to see light coming from the distant Universe and can
see black holes lying farther away.
-
- Distance in
the Universe can be measured by a quantity known as “redshift”; the higher an
object’s redshift, the more distant it is and the earlier it appears in the
Universe’s history. Many of JWST’s newfound black holes lie at redshifts of
between 4 and 6, which corresponds to a time when the Universe was about 1
billion to 1.5 billion years old.
-
- In JWST
images, these faint black holes appear as small and fairly unimpressive blobs,
but “they are clearly different” from the galaxies surrounding them. JWST has discovered roughly ten times as
many faint black holes at these intermediate redshifts than would be expected
on the basis of the number of black holes previously known.
-
- The
confirmed record holder sits at the heart of a well-studied galaxy, called
GN-z11, which has a redshift of 10.6.
-
- This
suggests that as early as 400 million years after the Big Bang, the seeds for
black holes had already formed and were able to create a supermassive object.
Upcoming observations aim to probe the details of how superheated gas flows
around GN-z11.
-
- The most
distant active supermassive black hole to date found within galaxy CEERS
1019. It was detected because of the gas
and other matter whirling around them. The black hole is more than 13 billion
light-years from Earth.
-
- JWST also
spotted a black hole at a redshift of 8.7, in the galaxy CEERS 1019. This black
hole somehow managed to accumulate 9 million times the mass of the Sun in the
first 570 million years of the Universe.
-
- This would
violate the maximum rate at which black holes can grow, according to theory.
But JWST observations suggest that some black holes, such as the one in GN-z11,
might grow in this way, and that the theory might need revising.
-
- Based on
the Gravity Wave signal, the event was thought to be the result of a kilonova,
where two neutron stars merge (or a neutron star and a black hole), releasing a
tremendous amount of energy and gravitational waves in the process.
-
- The spectra indicated that the source was
about 10 billion light-years distant, whereas the Gravity Wave signal was
detected less than 0.5 billion light-years away. The key discovery was when the ultraviolet
spectrum from Hubble ruled out a Galactic origin.
- This resulted from an SMBH that consumed
surrounding material suddenly and rapidly. It was confirmed by optical and
infrared data that previously detected a red galaxy in the vicinity, and the
location of the bright burst is consistent with the galaxy’s center.
-
- The UV spectra showed absorption features
consistent with a huge release of energy, which pushed and was absorbed by gas
and dust surrounding the black hole. Combined with its brightness, the data
revealed that J221951 is one of the most dramatic events ever seen where a
black hole suddenly “switched on.”
-
- This discovery is part of a growing body of
research that shows how SMBHs play a very active role in a galaxy’s star
formation. As these behemoths gobble up material, such as gas, dust, and even
stars, they release intense bursts of energy that disrupt star-forming material
within the galaxy’s central region and disk
-
- They have identified two possible
mechanisms that could explain the sudden and voracious feeding behavior. On the
one hand, it is possible that an orbiting star passed close to the SMBH and was
pulled apart, known as a tidal disruption event (or more commonly as “spaghettification”).
-
- A second possibility is that J221951 is an
active galactic nucleus (AGN), known as a “quasar,” that began feeding on its
accretion disk. The SMBH at the center
of this galaxy “woke up” from its previously dormant state.
-
- In the future, we will be able to obtain
important clues that help distinguish between the tidal disruption event and
active galactic nuclei scenarios. For instance, if J221951 is associated with
an AGN turning on we may expect it to stop fading and to increase again in
brightness, while if J221951 is a tidal disruption event we would expect it to
continue to fade.
-
-
August 31, 2023 BLACK
HOLES – many mor found? 4135
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--------------------- --- Thursday, August 31,
2023
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