- 3072 - BLACKHOLES - supermassive but hard to detect? Astronomers have found the biggest blackhole ever measured. It is 40 billion times the Sun’s mass, or two-thirds the mass of all stars in the Milky Way. This blackhole is in a galaxy that’s supermassive itself and probably formed from the collisions of at least eight smaller galaxies.
--------------- 3072 - BLACKHOLES - supermassive but hard to detect?
- The galaxy “Holm 15A” is a huge elliptical galaxy at the center of a cluster of galaxies called “Abell 85“. Astronomers captured a snapshot of Holm 15A’s stars in orbit around the galaxy’s central blackhole and created a model to calculate the central blackhole’s mass.
-
- Making monster galaxies is when two spiral galaxies, like our Milky Way and the nearby Andromeda Galaxy, collide, and merge to form an elliptical galaxy. In crowded environments like galaxy clusters, these elliptical galaxies can collide and merge again to form an even larger elliptical galaxy. Their central blackholes combine as well and make larger blackholes, which can kick huge swaths of nearby stars out to the edges of the newly formed galaxy.
-
- The resulting extra large elliptical galaxy usually doesn’t have much gas from which to form new stars, so its center looks bare after its blackhole kicks out nearby stars. Astronomers call these huge elliptical galaxies with faint centers “cored galaxies.” Massive cored galaxies often sit in the centers of “galaxy clusters“.
-
- Holm 15A, the enormous galaxy at the center of its home galaxy cluster, must have formed from yet another merger of two already huge cored elliptical galaxies. That would mean Holm 15A probably formed from the combination of eight smaller spiral galaxies over billions of years.
-
- Pairs of spiral galaxies form elliptical galaxies, pairs of those ellipticals form “cored elliptical galaxies“, and a pair of cored galaxies formed Holm 15A. This series of mergers also created the blackhole in its center, a monster about as big as our solar system but with the mass of 40 billion suns.
-
- Distant galaxies with massive central blackholes that emit huge amounts of light as they gobble up nearby matter in a process called “accretion.
-
- This stellar mass blackhole appears to be 68 solar mass which is nearly three times bigger than the heaviest such objects should be, according to current thinking.
-
- Calculations suggest that the Milky Way galaxy's stellar-mass blackholes, which form after the violent deaths of giant stars, should be no greater than 25 times the mass of the sun. Supermassive blackholes that lurk at the hearts of galaxies are much bigger containing millions or billions of solar masses.
-
- This huge blackhole is 13,800 light-years from Earth, a small fraction of the Milky Way's estimated diameter of 200,000 light-years.
-
- Blackholes of such mass should not even exist in our galaxy, according to most of the current models of stellar evolution. Astronomers thought that very massive stars with the chemical composition typical of our galaxy must shed most of their gas in powerful stellar winds, as they approach the end of their life.
-
- Therefore, they should not leave behind such a massive remnant. Most blackholes are found via their dramatic activity in X-rays or gamma rays, which are emitted as the blackholes gobble up nearby gas and dust.
-
- Astronomers sought out stars that are orbiting inactive blackholes, which are apparent only by their gravitational pull. They discovered a star called “LB-1“, which is eight times the mass of the sun and appears to orbit a blackhole every 79 days, even though the blackhole isn't visible.
-
- New tools are being added to the research. The “Laser Interferometer Gravitational-Wave Observatory” (LIGO) and “Virgo’ gravitational-wave detectors have begun to catch ripples in spacetime caused by collisions of blackholes in distant galaxies.
-
- The mass of the blackhole depends on its calculated distance. Europe's “Gaia space telescope“, which precisely measures the movements of a billion stars, has suggested that the distance to this blackhole might be only about 7,000 light-years, or roughly half the distance preiously calculated. If that's true, the blackhole would be only 10 times the mass of the sun, not 25 solar mass.
-
- If LB-1 were closer, it would be less luminous and less massive and its observed temperature cannot be explained with less luminosity. Also, the discrepancy with Gaia's data could be explained if the star were excessively wobbling around the blackhole.
-
- We have a supermassive blackhole lurking at the center of our galaxy, called Sgr A*, which has a mass of about 4 million times that of our Sun.
-
- Surrounding Sgr A* is a dense cluster of stars. Precise measurements of the orbits of these stars allowed astronomers to confirm the existence of this supermassive blackhole and to measure its mass.
-
- For more than 20 years, scientists have been monitoring the orbits of these stars around this supermassive blackhole. Almost every galaxy, including our Milky Way, has a supermassive blackhole at its heart, with masses of millions to billions of times the mass of the Sun.
-
- When the universe was about 100 million years old, to the era of the very first galaxies. They were much smaller than today’s galaxies, about 10,000 or more times less massive than the Milky Way. Within these early galaxies the very first stars that died created black holes, of about tens to thousand the mass of the Sun.
-
- These massive blackholes sank to the center of gravity, which is the heart of their host galaxy. Since galaxies evolve by merging and colliding with one another, collisions between galaxies result in supermassive blackhole pairs. The bigger blackholes then collide and grow in size as well. A blackhole that is more than a million times the mass of our sun is considered “supermassive“.
-
- The two supermassive blackholes orbiting each other, and at the same time, each is exerting its own pull on the stars around it. The gravitational forces from the blackholes pull on these stars and make them change their orbit. After one revolution around the supermassive “blackhole pair“, a star will not go exactly back to the point at which it began.
-
- Using a well-studied star, S0-2, which orbits the supermassive blackhole that lies at the center of our galaxy every 16 years, we can already rule out the idea that there is a second supermassive blackhole with mass above 100,000 times the mass of the Sun and farther than about 200 times the distance between the Sun and the Earth.
-
- But, that doesn’t mean that a smaller companion blackhole cannot still hide there. Such an object may not alter the orbit of SO-2 in a way we can easily measure.
-
- The proximity of the Milky Way’s galactic center, 24,000 light-years away, provides a unique laboratory for addressing issues in the fundamental physics of supermassive black holes. The detection of a pair of supermassive blackholes in the galactic center would indicate that the Milky Way merged with another, possibly small, galaxy at some time in the past.
-
- Measurements of the star S0-2 also allowed scientists to carry out a unique test of Einstein’s general theory of relativity. In May, 2018, S0-2 zoomed past the supermassive blackhole at a distance of only about 130 AU, 130 times the Earth’s distance from the Sun.
-
- According to Einstein’s theory, the wavelength of light emitted by the star should stretch as it climbs from the deep gravitational well of the supermassive black hole.
The stretching wavelength that Einstein predicted that should make the star appear redder was detected and proves that the theory of general relativity accurately describes the physics in this extreme gravitational zone.
-
- The second closest approach of S0-2, will reoccur in about 16 years. If there are two massive blackholes orbiting each other at the galactic center, they will emit gravitational waves.
-
- Since 2015, the LIGO-Virgo observatories have been detecting gravitational wave radiation from merging stellar-mass blackholes and neutron stars.
-
- Any waves emitted by our hypothetical blackhole pair will be at low frequencies, too low for the LIGO-Virgo detectors to sense. But a planned space-based detector known as LISA may be able to detect these waves which will help astrophysicists figure out whether our galactic center blackhole is alone or has a partner
-
- Virtually every other galaxy bigger than our Milky Way has a supermassive blackhole at its center. These supermassive blackholes can weigh tens of millions of times more than our sun.
-
- Galaxy blackholes start small, when a galaxy is still young and regularly gobbling up groups of neighboring stars. As large stars die and collapse into blackholes, those black holes consume stars and even other blackholes, growing bigger and bigger as they go from small to intermediate to gigantic, like an enormous cosmic rolling snowball.
-
- Or, that might not be how it happens at all. Instead, supermassive blackholes might form from a runaway chain reaction of colliding stars. We are not sure?
-
- The process remains poorly understood. And it’s tough to study because simply finding the weight of a supermassive blackhole is time-intensive and hard to do from millions of light-years away.
-
- There may be another way to indirectly measure a supermassive blackhole’s size and gather more information on how they form. A spiral galaxy’s shape may give away clues to the size of its central blackhole, as well as its overall mass of stars and dark matter content.
-
- To investigate further, astronomers have launched “Spiral Graph“. This project aims to measure how spiral arms wind in thousands of distant galaxies. First, users confirm that each galaxy they’re shown is indeed a spiral. Then, they draw lines to sketch out its shape. These lines measure how tight or open the spiral galaxy’s arms are.
-
- Tight spiral arms suggest a large supermassive blackhole. Open spiral arms indicate a more modest blackhole.
-
- In a study published in March, 2021, Spiral Graph users were actually better at tracing galaxy shapes than algorithms were. The algorithms in software struggle to know where spirals begin and end, something humans don’t have a problem with.
-
- These citizen scientists have proven to be more accurate than computers. And combining the results from humans and AI, artificial intelligence, can boost confidence in the results.
-
- Their effort doesn’t only look at the pitch of spiral arms; volunteers are also chronicling the structure of galaxies and whether they’re merging with another galaxy. So even if the correlation between spiral arm shape and supermassive blackhole size doesn’t pan out, they’ll still have advanced the understanding of galactic evolution in other ways.
-
- Stay tuned, there is still more to learn. You too can become a citizen scientist. Here are more reviews available:
-
- 3066 - BLACKHOLES - mysteries left to be solved? Regardless of where or how they’re found, primordial blackholes could tell astronomers a lot about the universe we live in. Depending on their mass, they could serve as probes into galaxy evolution, high-energy physics, and even the earliest fractions of a second after the universe was birthed.
-
- 2945 - BLACKHOLES - that can not be explained? In October, 2020, the LIGO/Virgo collaboration published its latest batch of data, bringing the running total to 47 blackhole mergers, including two more that seem to feature at least one blackhole in the mass gap. And, a new gravitational-wave observatory in Japan, KAGRA, ran for two months earlier this year.
-
- 2929 - BLACKHOLES - history of discovery
-
- 2885 - BLACKHOLES - pictures and theories.? 100 years ago, Albert Einstein’s theory of General Relativity predicted that blackholes should exist. In 1960 physicist John Wheeler coined the name ‘blackhole’ and the study of these mysterious objects became a cottage industry in theoretical physics and astrophysics.
-
- 2883 - BLACKHOLES - Black holes are scary? If you fell into a black hole left over when a star died, you would be shredded. The massive black holes seen at the center of all galaxies have insatiable appetites. Black holes are places where the laws of physics are obliterated.
-
- 2593 - BLACK HOLE - new techniques to study? In 2019 astronomers unveiled the first direct picture of a black hole. Now, astronomers have used a different technique involving x-ray “echoes” to peer even closer the edge of a black hole
-
- 2573 - BLACKHOLES - everything we know? Blackholes are some of the strangest phenomena in our universe. One natural question to ask is how does Albert Einstein’s theory describe space and time around a massive spherical object like a star? The solution to this was found by Karl Schwarzschild. It is valid all around any static round object and, remarkably, only depends on its mass. That alone can define a black hole.
-
- 2461 -- BLACKHOLES - first discoveries? Astronomers have discovered a strange black hole-star pair, a finding that could open our eyes to millions of new black holes that have been hidden in the cosmos. Astronomers have assumed that there are millions of these black holes in our Milky Way galaxy alone.
-
- 2433 - Dark matter and blackholes.
-
- 2338 - It is easy to claim you took a picture of a black hole because there is nothing to see. Its not just black it is blank. But, astronomers claim they have taken that first picture. What they took was a picture of the hot visible accretion surrounding the Black hole. But, it is a first! Here is how it was done:
-
- 2331 - How the picture was taken? Actually, we can not see a black hole because no light escapes to see it with. You can not see a shadow either but you see the boundary of light round it. This is how we “see” a black hole . We see the accretion disk of hot material emitting light surrounding the black hole. We see the boundary not the black hole itself. It was not easy but here is how astronomers saw their first black hole
-
- 2090 - Blackholes and white holes?
-
- 2022 - Blackholes how to measure their mass? The more distant galaxies are more challenging. New techniques must be used to measure radius and rotation because they are so far away. A breakthrough was the finding of two blackholes orbiting each other
-
- 2020 - Blackholes, when did they first appear? How did the first stars form and how did they create the first blackholes, called quasars? How old was the Universe when these first stars happened? How are colliding blackholes and detecting gravitational waves helping in our understanding the birth of the universe?
-
- 1936 - Are there rogue Blackholes? Could primordial Blackholes be roaming our galaxy and could they explain the 26% of Dark Matter in the Universe? Massive Blackholes are at the center of most galaxies. Could smaller Blackholes be at the center of dwarf galaxies? Gravitational waves may be the new way to find some answers.
-
- 1918 - Blackholes and Galaxies? How do galaxies evolve? Which came first the central Black hole or the galaxy? Is there a direct correlation between the size of the central Black hole and the size of the galaxy ?
-
- 1908. - How the mass of a black hole is calculated?
-
- 1926. - Are there rogue blackholes wandering through our galaxy? Are there blackholes that we calling Dark Matter?
-
- 1891 - The Black hole is inescapable for stars greater than 20 Solar Mass. Blackholes are the evolution of natural stages in physics and astronomy. They are inevitable outcomes of interactions of mass and energy in the Universe. The mystery remains, what happens after the Black hole?
-
March 2, 2021 BLACKHOLES - supermassive? 3072
----------------------------------------------------------------------------------------
----- 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, March 2, 2021 ---------------------------
No comments:
Post a Comment