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Questions tagged [supermassive-black-hole]

Questions regarding the most massive examples of black holes that typically reside at the centers of galaxies.

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Is the hypothetical '(Don) Page curve' of evaporating black holes equal in time, so to speak, on both sides of the curve?

I have heard that Hawking radiation is slow at first, but rapidly increases when the black hole becomes much smaller... (I forget the formula...) Does that mean that the second half of Page's curve, ...
Kurt Hikes's user avatar
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2 votes
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How bright in the night sky would J0529-4351 (brightest quasar ever found) be if it were in our galaxy?

According to this article, the quasar (black hole) named J0529-4351 is the most luminous object in the known universe, being: 500 trillion times more luminous than the Sun To put it in terms easier ...
Ahmed Tawfik's user avatar
2 votes
3 answers
563 views

How can Kerr black holes have a 'speed limit' to how fast they can spin?

Obviously, the speed of light is a presumed limit, at least for 'physical' objects moving 'within' ('through'?) spacetime, but... In recent news some scientists believe they have figured out the ...
Kurt Hikes's user avatar
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What is a "Gentle Giant" Black Hole?

I have seen articles about the Milky Way's "gentle giant" black hole. For example: https://nypost.com/2022/05/12/image-of-gentle-giant-black-hole-at-milky-ways-center/ https://www.reuters....
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ER=EPR and information fuelling cosmic expansion

I apologize in advance for the lack of education, I'm a Canadian hillbilly. I was considering the concepts of ER=EPR and the growth of the black hole's internal system with the addition of information ...
ChristainJP's user avatar
4 votes
2 answers
181 views

Is it possible to detect gravitational lensing of both light and gravitational waves originating from the same event?

Is it theoretically possible to detect gravitational lensing of both light and gravitational waves, when both originate from the same source/event (merger of two stellar black holes or merger of two ...
Alex's user avatar
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Could the revolution of super-massive black holes around each other create a pulsar-array gravitational wave signal despite 'final parsec' problem?

Some commentators on the recently-observed very-long-wavelength gravitational wave signal involving pulsars, like Dr. Becky Smethurst, have implied that it might not be merging supermassive black ...
Kurt Hikes's user avatar
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Could macroscopic primordial black holes have created metals shortly after the big bang?

After seeing articles about the JWST like these two: https://news.cornell.edu/stories/2023/02/astronomers-discover-metal-rich-galaxies-early-universe https://www.livescience.com/james-webb-space-...
Nathan Stanton's user avatar
10 votes
2 answers
2k views

What is the mechanism through which mass is converted to thermal energy in the accretion disc of a black hole?

In the book The Cosmic Perspective, it is stated that as matter is falling into a supermassive black hole, up to $40\%$ of its mass are converted to thermal energy, making the accretion of matter ...
Vercassivelaunos's user avatar
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If black holes contain dark energy would the expansion of the universe be uniform?

Because black holes are different sizes presumably they would contain different quantities of dark energy and so some galaxies would accelerate faster in some directions than others. Dark energy from ...
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Did the Grus star get expelled from the Milky way because it was accelerated by the Sagittarius A black hole?

On Wikipedia there is an article that says a star may have been expelled from the Milky Way because it interacted with Sagittarius A. Sagittarius A* from Wikipedia: In July 2019, astronomers reported ...
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Does the (relative) distance of the photon sphere from the center of a black hole vary according its mass?

I know that the photon circle or photon sphere is located at around 1.5 times the radius of the Schwarzschild event horizon, but wouldn't it be comparatively further out for smaller black holes? After ...
Kurt Hikes's user avatar
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6 votes
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549 views

What do the symbols signify in Dr. Becky Smethurst's radiation pressure equation for black holes?

In her most recent video, "An ULTRAMASSIVE black hole has been discovered in a BRAND NEW way!", as well as a previous video, "How massive can black holes get?", Dr. Becky Smethurst ...
Kurt Hikes's user avatar
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How does Very Long Baseline Interferometry work?

According to internet sources, this technique increases the effective diameter of the telescope, thus improving the angular resolution of the telescope. However I don't understand how this actually ...
Ambica Govind's user avatar
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402 views

What's the meaning of "hard supermassive black hole binary"?

In this paper, the authors state in the Introduction that A hard SMBHB [SuperMassive Black Hole Binary] can eject surrounding stars to transfer their orbital energy and angular momentum, which may be ...
Jim421616's user avatar
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Could we detect dark matter by black holes gaining unexplained mass?

Dark matter is said to interact only gravitationally, so it won't commonly form black holes by itself. But if a black hole is already there, and dark matter encounters the event horizon, it should go ...
Hene's user avatar
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What is the rotational speed of Sagittarius A*?

Sagittarius A* is the Milky Way's own supermassive black hole. Up till recently, I used to think that Sagittarius A* was a static black hole, i.e. It had no rotational speed at all. But after doing a ...
Alastor's user avatar
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15 votes
7 answers
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How did the Milky Way quasar not disrupt life on Earth?

According to most sources of information I have found (A Quora answer and books), when galaxies become quasars, they destroy all life in their host galaxy, as they output so much radiation that they ...
Alastor's user avatar
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3 votes
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Will the universe eventually merge completely into a single, enormous BH

I see other similar questions, but mine is more specific: If total merger into one BH is the ultimate endgame, then if the universe had no net angular momentum in the beginning, then wouldn't the ...
Paul's user avatar
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Do all black holes, including stellar-mass ones, rotate at nearly the speed of light? Also, what exactly does that do to their shape?

From what I understand, astrophysicists have known for almost a decade that supermassive black holes seem to spin at incredible velocities; nearly the speed of light... In fact, some of the outer ...
Kurt Hikes's user avatar
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1 vote
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How many massive black holes exist in AGN-type galaxies?

Most galaxies have a massive (i.e., $m \gtrsim 10^5$ M$_{\odot}$) black hole in their center. Is it known 1) theoretically and 2) observationally what fraction of these massive black holes (maybe as a ...
Daddy Kropotkin's user avatar
4 votes
1 answer
73 views

What could cause a wind from an SMBH

In this paper, the author tests whether the Milky Way's Fermi bubbles could have been caused by an AGN-type explosion, or by a 'wind'. He comes to the conclusion that the wind may be "the same as ...
Jim421616's user avatar
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3 votes
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How do I create well a weighted black hole mass function?

I'm running a set of simulations to study the evolution of Super Massive black holes. In principle, I have the black hole masses and other property called merger tree weight in Mpc-3 unit which is ...
Matías Liempi's user avatar
10 votes
1 answer
2k views

Where is the barycenter of the Milky Way Galaxy?

Is the barycenter of the Milky Way Galaxy located within the supermassive black hole, or its event horizon, at the center of our galaxy?
Bob516's user avatar
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3 votes
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Why were only 4 days of data used in the M87 EHT observation?

I wonder why only 4 days of data were used in the M87 Event Horizon Telescope (EHT) observation. What is preventing you from obtaining a more detailed and clearer image over a longer period of time?
Aegean's user avatar
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2 votes
2 answers
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What does "energy dumped into waves" mean?

In A Very Short Introduction: Black Holes by Katherine Blundell, the author discusses the merger of two black holes in a binary system: The energy released in the merger of two supermassive black ...
Ahmed Samir's user avatar
1 vote
2 answers
128 views

Could primordial black holes explain the SMBH in the galactic centers?

If there were enough primordial black holes (with the right mass) they could explain dark matter. Could they explain the gargantuan monster holes in the center of galaxies?
Felicia's user avatar
3 votes
1 answer
144 views

Is the dark matter/baryonic matter ratio the same in galaxies with supermassive black holes?

My hypothesis is that if the ratio of dark matter/matter in galaxies with supermassive(weighing billions of suns) black holes are higher the black hole itself would be made of a large portion of dark ...
SuperFlyGuy's user avatar
8 votes
1 answer
365 views

Is the appearance of accretion disks of M87 and Sgr A* in EHT image, related to the nucleus being active or non-active?

I'm a newbie in this field so forgive me if I'm considering things wrong. As much as I can see, the newly published image of the Sgr A* looks pretty much the same as M87 released years ago. I'm ...
Tirdad Sadri Nejad's user avatar
9 votes
2 answers
926 views

Why is the ring in this simulation of Sgr A* off center?

In the recent releases of images of Sgr A*, simulated versions of what they expected were included along side the actual images they were able to get. What confuses me about these simulated images (...
Justin T's user avatar
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25 votes
3 answers
9k views

Why do some supermassive black holes have a * in their name?

Sgr A*, M87*,... Several supermassive black holes (SMBHs) at the center of galaxies have a star (*) in their name. But many others do not. Is there a physical difference between the SMBHs that are ...
usernumber's user avatar
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1 vote
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Can the Universe itself be a black hole? [duplicate]

Can the Universe be a Black Hole? Many years ago, after reading a book by Isaac Asimov (not a novel, but I forgot the title) I started wondering if it is be possible that the Universe itself is a ...
Joey Joystick's user avatar
2 votes
2 answers
150 views

What is the reason for Hercules A to emit huge fountains of Plasma?

Hercules A, a supermassive-blackhole situated in the galaxy 3C 348, emits Plasma as far as 1.5 million light years away !! Although the cause is poorly understood, what could be the possible cause for ...
Kavin Ishwaran's user avatar
5 votes
1 answer
125 views

Have any HCSSs (supermassive black holes with a tight bunch of gravitationally bound stars) ever been detected?

This article from sciencealert states: Astronomers think these two galactic cores could merge into one larger black hole, sending huge gravitational waves rippling out across spacetime. But if there'...
Alex's user avatar
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Image of the black hole [duplicate]

The first ever image of a black hole shows a circular black central portion surrounded by an illuminated accretion disk. If a black hole wraps spacetime completely around it, then in any direction it ...
Mohan Mone's user avatar
2 votes
2 answers
153 views

Does the density of a black hole decrease after releasing a large amount of Hawking radiation?

Is is true that the smaller a 'regular', stellar-mass black hole is, the denser it is inside of its event horizon? After all, if you look up (or calculate) the Schwarzschild radii of the Sun and the ...
Kurt Hikes's user avatar
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0 votes
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178 views

Is gravity affected by time dilation? [closed]

I just thought about what time realy is but I can't put my head around this so I was thinking that if time dilation happens at the edge of a black hole that just everything gets slower. But does ...
somedude324334's user avatar
2 votes
2 answers
146 views

Could quasars be interior to the event horizon of a SMBH?

My question is prompted by suspicion of three current ideas in astrophysics: GR predicts a singularity at the center of a BH without regard to QM. quasar hyper-luminosity is caused by an acretion ...
Henry's user avatar
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5 votes
3 answers
1k views

Could a black hole's accretion disk be bright through natural means?

This question is based on this description of the Cormoran Supermassive Black Hole in the Orion Arm's website: Surrounding this event horizon is an (apparently artificial) accretion disk about 4AU in ...
JohnWDailey's user avatar
1 vote
0 answers
36 views

From where the light comes? [duplicate]

Gravitational field of a supermassive blackhole is so strong that even light cannot escape from it (eg. black hole in the core of M87). In this case when a blackhole tears a star,a bright disk of ...
Kavin Ishwaran's user avatar
6 votes
1 answer
260 views

Has gain in mass from accretion onto a black hole been observed?

Have we observed a black hole directly gain mass via accretion? That is, have we observed the black hole to have mass $m_1$ at time $t_1$ and then observed its mass to be $m_2 > m_1$ at a later ...
Daddy Kropotkin's user avatar
13 votes
4 answers
6k views

How can a black hole have a charge, or be charged?

So-called 'hairless' black holes (no-hair theory, or theorem?) , which is what real black holes are, can be described by just three characteristics: Mass, spin, and charge. It is easy enough to ...
Kurt Hikes's user avatar
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7 votes
1 answer
445 views

Why is the Milky Way's SMBH inactive?

Our galaxy is not an active galactic nucleus (AGN). With so many stars and so much gas orbiting it, as explained here Central kiloparsec of Seyfert and inactive host galaxies: a comparison of two-...
Jim421616's user avatar
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-2 votes
2 answers
155 views

Does black hole singularity really exists with respective to relative frame of reference? [duplicate]

How can one describe this phenomena? What are the factors that we should consider for solving such a problem?
Sivaditya Varma's user avatar
10 votes
2 answers
3k views

Can an entire star pass through the event horizon of a black hole unharmed?

Can there be any black hole big enough that a regular sized star can pass through its event horizon unharmed?
S. M. JAHANGIR's user avatar
1 vote
0 answers
38 views

What do stars in galaxies without supermassive black holes revolve around? [duplicate]

I still don't quite understand what the stars in galaxies without SBHs revolve around. I mean, the stars must orbit something. If the Sun suddenly disappeared, the planets wouldn't just continue in ...
Giovanni's user avatar
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4 votes
1 answer
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Could Sgr A* be a core of dark matter instead of a supermassive black hole?

A recent paper (related news) shows that Sgr A* at the center of the Milky Way galaxy could be a dark matter core, instead of a supermassive black hole, according to their calculation using the ...
NeutronCat's user avatar
10 votes
3 answers
2k views

How do we know that supermassive black holes can gain mass by means other than merging with other supermassive black holes?

I just stumbled across the following answer "update" from 2013: This just in, recent observations have ruled out the possibility that SMBHs gain mass only through merging with other black ...
uhoh's user avatar
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0 votes
1 answer
85 views

What is Hawking radiation? [closed]

Like the radiation the Sun gives out to sustain it's circular shape, will Hawking radiation sustain the black hole's shape?
yor's user avatar
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2 votes
1 answer
79 views

Would studying massive stars that are experiencing time dilation due to proximity to a black hole be useful?

I saw this question (Could a star closely orbit a black hole long enough for the star to have lost 0.5B+ years to time dilation?) and came up with an interesting thought. Massive stars live for less ...
WarpPrime's user avatar
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