- 3938 - GALACTIC BLACKHOLE - at center of our galaxy? The doomed cloud is 3,000 times longer than the distance from the Earth to the Sun. It provides clues to the strange and extreme environment around a black hole 4 million times more massive than the Sun.
-------- 3938 - GALACTIC BLACKHOLE - at center of our galaxy?
- 26,000 light
years away, a strange and enormous cloud is being stretched and strained under
the tremendous tidal forces of “Sagittarius A*”, the name of the supermassive
black hole at the center of our galaxy. In just 13 years, astronomers expect
this cloud, known as X7, to be torn to shreds by this extreme environment.
-
- When X7 was
first noticed in 2007, astronomers described it as a comet-shaped object close
to the galactic center. X7 was classed as a “G object”, a group of oddball
blobs of gas that orbit the supermassive black hole Sagittarius A* (Sgr A*) at
the center of the Milky Way that act like gas clouds when far from the black hole
only to hold together like stars as they draw closer in their orbits.
-
- X7 was
vastly more massive than any comet, about 50 times the mass of Earth. Over the
last decade-and-a-half, though, astronomers have been able to watch X7 stretch
and shift in real-time.
-
- In that
time, X7 grew twice as long as it once was, indicating that it is being
stretched out by Sgr A* like a noodle. It’s still relatively small and
relatively light, and that’s why it gets
stretched, because it’s vulnerable to the forces of the black hole.
-
- A filament
like X7 is an extreme object in an extreme environment. Even though it’s
traveling at 490 miles per second, its orbit around the supermassive black hole
at the center of the Milky Way would take 170 years if it were to complete it
successfully.
-
- It was only
created a few decades ago, and in a few decades, it’s going to be destroyed.
And a few decades, even a hundred years, is a very short timescale on
astronomical scales.
-
- When it was
first detected, astronomers thought it might be the result of a jet or wind
blown out from a nearby star, “S0-73”. But looking over data from the last 20
years, the team found the two aren’t moving in the same direction, nor are they
in quite the same three-dimensional volume.
-
- They
suspect X7 is the result of a close
scrape between two binary stars. In the extreme tidal environment around a
supermassive black hole, binary stars are common, and so are the collisions and
mergers between them. If two stars grazed against each other, a long stream of
gas and dust would be ejected from their violent collision, which would match
the shape and behavior of X7.
-
- Even though
it’s zooming around the center of our galaxy at tremendous speeds, X7 will be
ripped apart by Sagittarius A*’s tidal forces long before it completes its next
170-year orbit. In 2036, the team estimates, X7 will reach its “periapse
passage”, its closest approach to the black hole.
-
- Even though
X7 is zipping around Sagittarius A* 26,000 light years away (and its fate was
sealed about 25,987 years ago), that’s still 794,000 light years closer than
the next-closest supermassive black hole, in the dwarf galaxy Leo. This means
astronomers will have a close-up view of what happens to a gas cloud very close
to a supermassive black hole.
-
- Along with
the Keck telescopes used to observe it since 2002, the JWST is scheduled to
take a look at the Sagittarius A* and X7.
JWST observes in different spectra than the Keck observatory. This will give us insights into its
structure.
-
- Using
observations taken with the Atacama Large Millimeter Array (ALMA), a radio
observatory sited in Chile, astronomers have determined that the galaxy
“COS-87259”, containing this new supermassive black hole is very extreme,
forming stars at a rate 1000 times that of our own Milky Way and containing
over a billion solar masses worth of interstellar dust. The galaxy shines
bright from both this intense burst of star formation and the growing
supermassive black hole at its center.
-
- The black
hole is considered to be a new type of primordial black hole, one heavily
enshrouded by cosmic “dust”, causing nearly all of its light to be emitted in
the mid-infrared range of the electromagnetic spectrum. This growing supermassive
black hole is generating a strong jet of material moving at near light speed
through the host galaxy.
-
- Today, black
holes with masses millions to billions of times greater than that of our own
Sun sit at the center of nearly every galaxy. How these supermassive black
holes first formed remains a mystery for scientists, particularly because
several of these objects have been found when the Universe was very young.
-
- Because the
light from these sources takes so long to reach us, we see them as they existed
in the past; in this case, just 750 million years after the Big Bang, which is
approximately 5% of the current age of the Universe.
-
- What is
particularly astonishing about this new object is that it was identified over a
relatively small patch of the sky typically used to detect similar objects,
less than 10 times the size of the full moon, suggesting there could be
thousands of similar sources in the very early Universe. This was completely
unexpected from previous data.
-
- The only
other class of supermassive black holes we knew about in the very early
Universe are “quasars”, which are active black holes that are relatively
unobscured by cosmic dust.
-
- These
quasars are extremely rare at these distances similar to COS-87259, with only a
few tens located over the full sky. The surprising discovery of COS-87259 and
its black hole raises several questions about the abundance of very early
supermassive black holes, as well as the types of galaxies in which they
typically form.
-
- These
results suggest that very early supermassive black holes were often heavily
obscured by dust, perhaps as a consequence of the intense star formation
activity in their host galaxies.
-
- Astronomers
have also just discovered what may be the largest black hole known to
date. The giant black hole has a mass
of 30 billion suns and sits at the center of a galaxy located hundreds of
millions of light-years from Earth.
-
-
Astronomers discovered the black hole during observations of a galaxy
located farther away from Earth than the one centered around the monster black
hole, while using the gravity of the foreground galaxy to magnify the
background object.
-
- This
effect, known as gravitational lensing, is a result of gravity bending the
light around extremely massive objects. Serving as nature's own telescope,
gravitational lensing frequently helps astronomers to increase the
magnification of objects too distant to be properly visible to human-made
telescopes.
-
- This
particular black hole, which is roughly 30 billion times the mass of our sun,
is one of the biggest ever detected and on the upper limit of how large we
believe black holes can theoretically become.
-
- The team
arrived at the size of the black hole by analyzing the magnification of the
foreground object in a series of images taken by the Hubble Space Telescope.
Using sophisticated computer modeling, the scientists were able to simulate how
much light bends around the foreground galaxy where the black hole resides.
They tested thousands of black hole sizes before arriving at a solution that
matched the observations.
-
- Most of the
biggest black holes that we know about are in an active state, where matter
pulled in close to the black hole heats up and releases energy in the form of
light, X-rays, and other radiation.
-
-
Gravitational lensing makes it possible to study inactive black holes,
something not currently possible in distant galaxies. This approach could let
us detect many more black holes beyond our local universe and reveal how these
exotic objects evolved further back in cosmic time.
-
- An event
horizon marks the boundary at the outer edge of a black hole. The event horizon is the spherical outer
boundary of a black hole loosely considered to be its "surface."
-
- It is the
point that the gravitational influence of the black hole becomes so great that
not even light is fast enough to escape it. As a result of the fact that Albert
Einstein's theory of special relativity tells us that no signal can exceed the
speed of light in a vacuum humanity can never hope to obtain a signal from the
one-way boundary that is an event horizon.
-
- As such
event horizons effectively act as cosmic gatekeepers preventing us from ever
directly observing the secrets that lie at the heart of black holes. Yet they
can reveal a great deal about the environment around them.
-
- When an
item gets near an event horizon, a witness would see the item's image redden
and dim as gravity distorted light coming from that item. At the event horizon,
this image would effectively fade to invisibility.
-
- Within the
event horizon, one would find the black hole's singularity, where previous
research suggests all of the object's mass has collapsed to an infinitely dense
extent.
-
- This means
the fabric of space and time around the singularity has also curved to an
infinite degree, so the laws of physics as we currently know them break down.
-
- In a
distant galaxy, a supermassive black hole spewing radiation at near light speed
has shifted its angle by a whopping 90 degrees to point directly toward Earth,
a sharp turn that's puzzling physicists.
-
- Active
galactic nuclei (AGN) are the hungry black holes at the cores of many other
galaxies, and they accrete matter and spew powerful jets of high-energy
particles known as relativistic jets.
-
- “PBC
J2333.9-2343”, a large galaxy about 4 million light-years across, was
previously classified as a radio galaxy, meaning its AGN's gargantuan jets of radiation
were pointed perpendicular to our line of sight.
-
- But new
research reclassifies the galaxy as a blazar, meaning the black hole's jets are
now pointed directly at Earth. This means the galaxy's jets shifted by a
"dramatic" degree.
-
- The
relativistic jet of its supermassive black hole had changed its direction. It was observed across nearly the entire
electromagnetic spectrum, from radio waves to gamma-rays. Their observations
showed that this galaxy had characteristics typical of blazars: It brightened
and dimmed like a blazar, and it had similar jets. The object was most likely a
blazar.
-
- They also
observed two lobes, areas where an AGN's jets interact with surrounding gas,
where some jets had previously made their mark. This blazar's lobes are
"very old. These dormant lobes are
evidence that the jets have, in fact, changed direction.
-
- It's not
totally unprecedented for a galaxy's jets to appear in different places. But in
prior examples, there were two sets of lobes, meaning two separate jets turning
on and off.
-
- What caused
this great shift? Astronomers are still working that out. Current theories
include a galaxy merger, where another large galaxy collided with PBC
J2333.9-2343, jostling the orientation of everything within it. More
observations are needed to figure out this mystery.
-
March 21, 2023 GALACTIC BLACKHOLE
- at center of our galaxy? 3926
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--- Sunday, April 2, 2023
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