- 4529 - BLACKHOLES - discovered with gravity waves? - Albert Einstein didn't believe we'd be able to detect gravitational waves from the merger of two black holes. The James Webb Space Telescope finds ancient black holes. The most fascinating and mysterious objects in the cosmos are “black holes”. These pockets in the fabric of spacetime are anchored by an infinitely dense and infinitesimally small concentration of mass: a “Singularity”.
------------------------------------- 4529 - BLACKHOLES - discovered with gravity waves?
- We simply do not know what lies beyond a
black hole's event horizon, singularity, the boundary beyond which light can't
cross. In the 25 years since 1999, the
science of black holes has come on leaps and bounds, especially as it relates
to bringing them from their theoretical origins into observational reality.
-
- Like all black holes, supermassive black
holes at the hearts of galaxies are bounded by one-way, light-trapping surfaces
called “event horizons”. No light can
escape a black hole, and no black hole can really ever be “seen”. What can be
seen, however, is the shadow these voids cast on the glowing material
surrounding them. It is upon this material that black holes gradually feed.
-
- Capturing an image of a black hole is no
small feat. One project that endeavored
to do this is the Event Horizon Telescope (EHT), a global network of
observatories that coordinates to act like a telescope the size of Earth. In
April 2019, the EHT collaboration
revealed to the public that they had succeeded in imaging a black hole using
data collected in 2017.
-
- The object in question was the supermassive
black hole at the heart of the distant galaxy Messier 87 (M87). The black hole is located around 55 million
light-years away with a mass of about 6.5 billion suns, making it much more
massive than our galaxy's supermassive black hole Sagittarius A* (Sgr A*).
-
- At the heart of the Milky Way, our home
galaxy is the cosmic titan Sagittarius A* (Sgr A*), which was first detected in
strong radio waves by Karl Jansky in the 1930s and isolated to a more compact
region in 1974 by astronomers Bruce Balick and Robert L. Brown. By the 1980s,
astronomers had officially proposed this object was a tremendously large black
hole, but Sgr A* remained somewhat shrouded in mystery.
-
- That was until 2008, when astronomers
Reinhard Genzel and Andrea Ghez determined Sgr A* to be a supermassive black
hole with a mass 4.3 million times that of the sun. The discovery was
ingeniously made not by looking at Sgr A* directly, but by measuring the
velocity of fast-moving stars called the "S-group" that whip around
it.
-
- Tracking these stars over two decades,
looking at the signals of these stars as they approach this dark mass and leap
away from it, Genzel and Ghez were able to measure the mass and size of this
region to really great accuracy.
-
- Since then, astronomers have also
calculated the diameter of the Sgr A* to be around 14.6 million miles , which
is extremely tiny compared to the Milky Way itself, which is 100,000
light-years wide and 1,000 light-years thick.
-
- This discovery revealed that, like other
galaxies, the Milky Way revolves around a black hole with an almost
incomprehensible mass.
-
- On May 12, 2022, the EHT Collaboration
managed to reveal the first image of Sgr A* created using data collected in
2017. Despite Sgr A* being much closer to Earth, it was tougher to image
because the material surrounding it also races around at near light-speed, but
Sgr A* is much smaller than M87*, so full orbits were completed almost quicker
than the eye of the EHT could see.
-
- What's interesting about these two black
holes is that, although they're both supermassive black holes, they're also
quite different. M87* lives inside the
M87 galaxy, which is a giant elliptical galaxy. It's quite old. It's gone
through many mergers, and it's very large. On the other hand, Sgr A* lives in
our Milky Way, which is very common among galaxies and, in galactic terms, very
small. It's a spiral galaxy that's not that old.
-
- “J0529-4351” is a “quasar” powered by a
supermassive black hole that is located so far from Earth its light has taken
about 12 billion years to reach us. With a brightness equivalent to 500
trillion suns, this is the brightest quasar seen to date.
-
- Existing when the universe was less than 2
billion years old, J0529-4351 has a mass between 17 billion and 19 billion
suns, and it eats, or "accretes," at least one solar mass worth of
gas and dust every single day.
-
- Gravitational waves are tiny ripples in
spacetime caused when objects accelerate; they were first suggested to exist by
Albert Einstein's 1915 theory of gravity, general relativity. As binary black
holes spiral around one another, they set the fabric of space ringing with
gravitational waves. When they eventually collide, they create a high-frequency
screech of gravitational waves, then a final gravitational wave
"ringdown," lasting a fraction of a second.
-
- However, Einstein believed that even the
most intense gravitational waves would be too faint and emitted at a distance
too great to ever be detected on Earth. Yet, on September 14, 2015, the Laser
Interferometer Gravitational-wave Observatory (LIGO) detected the gravitational
wave signal “GW150914” from the merger
of stellar mass black holes about one billion light years away. The detection
proved Einstein's fears unnecessary, while the signal simultaneously proved his
theory of general relativity correct.
-
- Since 2015, LIGO and its collaborating
instruments, Virgo in Italy and KAGRA in Japan, have detected a multitude of
gravitational wave signals from colliding black hole pairs, merging neutron
stars, and even mixed mergers between black holes and neutron stars. Including seeing the ring-down signal, as
predicted from the theory of two solar mass black holes merging together.
-
- The discoveries discussed so far have
concentrated on supermassive black holes, or black holes that sit at the hearts
of galaxies and influence the realms' development. These cosmic titans are born
from a merger chain of increasingly larger and larger black holes. This means
they end up with incredibly huge masses.
-
- There are more diminutive black holes. Stellar-mass black holes are born when
massive stars, with about eight times more mass than the sun or more, run out
of the fuel supply needed for nuclear fusion in their cores and collapse,
triggering a supernova. The masses of
these black holes start at about five solar masses and range up to 100 solar
masses.
-
- That means there is a vast mass gap between
stellar mass black holes and supermassive black holes. But, in this gap, you'd
expect the intermediate-mass black holes to dwell. Yet, much less is known about
these medium-sized black holes, which should have a mass range of around a 100
solar masses to hundreds of thousands of solar masses.
-
- Several potential intermediate black hole
discoveries have been made over the last 25 years, including “GCIRS 13E” in
2004. This was suspected to be the first intermediate-mass black hole found in
the Milky Way galaxy, orbiting Sgr A* at a distance of around three light-years
away. This, like many other potential sightings of intermediate mass black
holes, has been disputed.
-
- The most well-founded evidence of the
existence of intermediate black holes came in 2020, when LIGO detected its
biggest gravitational signal to date. The source of the signal, designated
“GW190521”, was a merger of two stellar-mass black holes birthing a
142-solar-mass black hole located around 7 billion light-years away.
-
- Mergers of smaller black holes and black
holes feeding on surrounding matter to become bigger black holes should take
billions of years. Explaining large
black holes starts to get challenging is when we see black holes with millions
or billions of solar masses that existed before the universe was 1 billion
years old. Finding supermassive black
holes billions of years after the Big Bang is expected, but discovering them
around the time the first stars formed is more surprising.
-
- If scientists were worried when other
telescopes were turning up with results of supermassive black holes existing
800 million years after the Big Bang, they started getting very concerned when
the JWST found such ultramassive black holes as early as when the universe was
only 500 million to 600 million years old.
-
- The JWST launched just two years ago is
seeing what we think are supermassive black holes at very, very early
times. The observations it's making are
both electrifying and confusing. There are questions arising about black holes
because we're probing into regions of the universe we haven't probed before.
-
-
July 21, 2024 BLACKHOLES
- discovered with gravity
waves? 4529
------------------------------------------------------------------------------------------
-------- Comments appreciated and Pass it on to
whomever is interested. ---
--- Some reviews are at: -------------- http://jdetrick.blogspot.com -----
-- email feedback, corrections, request for
copies or Index of all reviews
--- to:
------
jamesdetrick@comcast.net
------ “Jim Detrick” -----------
--------------------- --- Tuesday, July 23, 2024
---------------------------------
No comments:
Post a Comment