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Questions tagged [black-hole]

Questions regarding points of extremely high mass density, which creates an extremely strong gravitational field from which light cannot escape.

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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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What exactly is a 'gravastar'? How is it different from a 'regular' black hole?

The Wikipedia article on gravastar says that it has a 'regular' black hole metric (Schwarzschild, I presume?) on the outside, but a de Sitter metric on the inside.... What exactly does that mean? Don'...
Kurt Hikes's user avatar
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Spinning black holes and ring singularities

2 days ago, I asked this question on the physics stack exchange: https://physics.stackexchange.com/questions/815217/what-happens-to-the-ring-singularities-when-two-kerr-black-holes-merge?. However, ...
Flamethrower's user avatar
4 votes
1 answer
830 views

Stellar Mass Black Holes and the companion star dynamics

I was studying stellar mass black holes and wondered why almost all of them had a companion star, I came through many explanations but was not satisfied, is it because its hard to detect them without ...
Bhavya Singh's user avatar
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2 answers
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Does an infalling observer ever cross the black hole event horizon in finite proper time?

I am interested in how an infalling observer perceives the plunge into a black hole. Let me assume that actually we have three spaceships: C being at a constant distance to the event horizon, and A ...
Zweistein's user avatar
4 votes
1 answer
2k views

Evolution of black holes. Could they lose mass faster than the Hawking radiation?

As far as I understood the biggest black holes we know are at the centre of very distant quasars and they are enormous. All the big black holes are very far away. At the centre of the closer galaxies ...
FluidCode's user avatar
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3 answers
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Black Hole Photon Ring

NASA recently published a video simulation of what it would look like flying into a black hole (video can be seen here ). What confuses me is that it appears to show the photon ring around the black ...
Jan Stuller's user avatar
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1 answer
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Does nucleosynthesis such as R Process, S Process, and P process occur in relativistic jets?

By answering a recent question about relativistic jets and their cooling I became more curious about relativistic jets. This might be a totally another sub topic on relativistic jets. But I was ...
Arjun's user avatar
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2 votes
1 answer
135 views

Why are black holes oblate spheroids?

I just heard something I have heard a million times before: "The shape of a spinning black hole is an oblate spheroid." This time, it hit me as odd that a black hole's shape changes with a ...
Curious Layman's user avatar
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Have measurements been conducted on the position of the galactic center of mass and the orbit of the presumed black hole at the center?

Related questions have been raised before Is our central black hole actually at the CG of the galaxy? Orbiting supermassive black hole or galactic center of mass? , where explanations have been given ...
Imyaf's user avatar
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Does a relativistic jet contain dust particles?

Black-holes accreting matter can emit jets of plasma that can exceed half the speed of light. Can these jets cool off enough that dust particles condense in them? If so, could we detect flashes of ...
Kevin Kostlan's user avatar
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1 answer
158 views

A couple of questions on Hawking radiation

Black holes progressively evaporate due to the emission of Hawking radiation just outside their event horizon primarily in the form of photons. However, there is a small probability that they emit ...
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Moon mass object hitting Earth vs Moon mass blackhole hitting Earth damage comparison

Doesn't a blackhole do less damage if it goes fast enough to be able to escape fast enought but a moon-mass object if going faster does more damage? Is this true or would a black hole do more damage?
MiltonTheMeme's user avatar
2 votes
1 answer
117 views

How ultra massive black holes would " disrupt the accretion discs that feed them" beyond some upper limit to their masses?

According to this, How big could a black hole get recent studies suggest that UMBHs cannot physically grow much beyond this (10 billion solar masses) anyway, since they would then begin to disrupt ...
Pablo's user avatar
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My question is about the warp of time and space near black holes

I have seen some recent articles indicating that there might not be a singularity at the center of black hole at all1. Have further heard commentary about black holes that spin incredibly fast. I was ...
Charles Creel's user avatar
3 votes
2 answers
210 views

Black hole explosion due to rotation [duplicate]

I am not an expert, I was just thinking about this scenario: A black hole that, for some reason, will start spinning faster and faster. Is it theoretically possible that the rotation becomes so fast ...
Nicola Lepetit's user avatar
2 votes
3 answers
313 views

Is there evidence against a Universe Black Hole?

As far as I know, the critical density of our observable universe coincides with the density of a huge black hole of the same radius. It could be a BH expanding at the speed of light and growing in ...
Juan Casado's user avatar
6 votes
2 answers
1k views

What are the most up to date, accepted, evolution stages of big stars that end in compact objects or a planetary nebula?

There are numerous charts and diagrams showing the stages of stellar evolution, as: or among many more (you can find several after googling a little), for example. When I studied my B.Sc. on Physics,...
omivela17's user avatar
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What would happen if a low-mass primordial black hole was captured by a brown dwarf or planet mass object?

Prompted by a recent PBS SpaceTime video The video in question discusses what would happen if a low-mass (asteroid-mass) primordial black hole were captured in the core of a Sun-like star (a so-called ...
asgallant's user avatar
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How long could a world like the Moon survive with an Earth mass black hole in the center?

I asked that question at the worldbuilding stack exchange. https://worldbuilding.stackexchange.com/questions/202273/how-long-could-a-planet-or-moon-survive-if-it-had-an-earth-mass-black-hole-withi ...
M. A. Golding's user avatar
21 votes
4 answers
6k views

What would happen if a small black hole fell into a star?

Let's say you created a cannon that can shoot small black holes and you shoot it at some star. Would the star just turn into a black hole silently? Or rather first destabilize and produce a last ...
Filip Sondej's user avatar
6 votes
1 answer
804 views

Could an hypothetical hidden black hole companion to the sun be revealed by proper motion data?

If the Sun were in a binary star system with a black hole companion, the Sun would be orbiting the black hole, and this should be reflected in a change in the observed proper motion of nearby stars. ...
tutizeri's user avatar
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Why do we not call black holes black stars or dark stars?

I've never understood why the term black holes are widely used to describe what is actually a black star or dark star. I mean why name something just because of its extreme space curvature effects? In ...
eBookworm's user avatar
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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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-2 votes
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Can black holes even exist [if mass cannot be retained near the collapse threshold]?

A black hole happens because enough material mass exists in an area to create a gravitational field strong enough that nothing escapes (including light). This gravity also exceeds the strength of ...
hamstar's user avatar
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1 answer
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Amount of black holes over time

Hello the number of black holes is much bigger than the number of black holes in the past right?Let $b$ be the number of black holes in the universe.Obviously $\frac{db}{dt}>0$ but what about $\...
Root's user avatar
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2 votes
0 answers
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JWST Early Black Holes: Gas Collapsed To Metallic Hydrogen Core?

I was reading an article about early black holes found by JWST at Redshift 9. And saw that there was wonder at how large amounts of gas could collapse into a black hole as a theory. So my question is ...
WiFiSunset's user avatar
10 votes
2 answers
626 views

Are gravitational waves emitted equally in all directions?

I have a question regarding gravitational waves that I can't figure out. Hope some wise minds here can help a simple amateur without technical or scientific education. Two black holes rotating around ...
Peter's user avatar
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2 votes
1 answer
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Black hole collision

In a situation where 2 black holes are close to colliding, but do not collide, can one black hole free/steal matter from the other in passing if the event horizons brush?
Shaun Eric Ewing's user avatar
23 votes
3 answers
4k views

From an outsider's perspective, how can a black hole grow if nothing ever crosses the event horizon?

Due to time dilation, an outside observer never sees a falling object actually cross the event horizon. I'm not referring to the optical illusion of red-shifted light making objects appear to fade ...
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2 answers
157 views

Possibility for black holes having negative energy

new to the community here. The question I have is whether black holes can possibly contain negative energy of any sort? It’s not a carefully thought-out question as space is not my bailiwick.
Bill Joe's user avatar
3 votes
4 answers
3k views

How do stars 1 billion times the volume of our sun form and can they become black holes?

UY Scuti is a star 1 billion times the volume of our sun. A billion solar mass black hole formed 750 million years after the Big Bang. Could it have formed from a star like UY Scuti? Rare black hole ...
user avatar
7 votes
2 answers
3k views

Is there a limit to the Schwarzschild radius?

The Schwarzschild radius is a way for us to calculate the extent to which something has to be shrunk in order for it to become a black hole but I was wondering is there a limit to the object that we ...
Shubhankar Dixit's user avatar
1 vote
1 answer
106 views

Death of a Black Hole ≠ Rebirth?

So we all know that Stephen Hawking proved that Black Holes do evaporate overtime through hawking radiation. But that energy is released in very discrete amounts and there will be a time in the ...
Shubhankar Dixit's user avatar
0 votes
1 answer
121 views

Will an overspun black hole be white?

I recently watched a Kurzgesagt video about destroying black holes. In the video, they mentioned that you can (theoretically) "overspin" a black hole to remove its event horizon, thereby ...
Seggan's user avatar
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5 votes
1 answer
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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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Question about how it's possible for black holes to have gravity and a possible resolution [duplicate]

1. Assumptions 1.a: gravity propagates at c (maximum) 1.b: gravitational fields cause time dilation 1.c: escape velocity at the event horizon is c 1.d: gravity "warps" space-time, but in ...
P Varga's user avatar
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1 vote
1 answer
305 views

The event horizon of a black hole

According to https://www.nationalgeographic.com/magazine/article/black-holes-einstein-star-eaters', when something crosses the event horizon of a black hole "A person watching from the outside ...
Ph1ra's user avatar
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9 votes
1 answer
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If you were on a planet orbiting a star that has a black hole companion, could you see light from your host star bent 180 degrees?

I realize that there is a distance from a black hole where photons can orbit. I understand that this orbit is very unstable, but I am concerned with photons just outside this range. Could the black ...
Jack R. Woods's user avatar
1 vote
0 answers
77 views

Could both the high incidence of supermassive Black Holes (BH) and the expansion of the universe be consequences of vacuum entanglement energy?

The notion that spacetime may emerge from entanglement between factors comprising a Hilbert space decomposition of the vacuum has been suggested by many (for example, M. Van Raamsdonk “Building up ...
RalphW's user avatar
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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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3 votes
1 answer
105 views

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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1 vote
1 answer
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How do primordial black holes are able to have an event horizon?

How do primordial black holes have an event horizon? Sorry for the stupid question, but I know primordial black holes have just a handful of mass in a cosmic scale compressed in a singularity. But if ...
Artur Carneiro Barroso'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
19 votes
2 answers
3k views

Could we (Earth, Humanity, Solar System) be falling into a black hole?

With the expansion of the universe, all objects far away from us appear to be moving away (ie: exhibit Redshift). With distance, this acceleration / redshift also seems to increase (~73,000 (m/s) / (...
G. Putnam's user avatar
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3 votes
1 answer
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Can a quasi-star develop a stable crust?

Could a quasi-star potentially develop a stable outer layer or crust during its early stage of formation if it were to be bombarded with substantial amounts of matter, coexisting with its core and the ...
Sandro Kakhetelidze's user avatar
1 vote
1 answer
130 views

Could You Escape an Event Horizon by increasing a Black Hole's velocity?

I have an idea for trying to escape the black hole's event horizon that might make basically no sense and I want it double checked. Basically, I do know that you can't escape the event horizon unless ...
skout's user avatar
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1 vote
1 answer
223 views

Will the Sun fall into a black hole? If so, when and which one?

According to the Wikipedia page "Timeline of the far future", stellar remnants not ejected from their galaxies will fall into the central supermassive black holes over a time scale of around ...
qdinar's user avatar
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4 votes
1 answer
981 views

Which wavelength is most likely to be emitted over the lifetime of a black hole by hawking radiation and which is most likely at any given time?

What equations tells us the most likely wavelength emitted for a given black hole mass at any instant in time and over the whole life of the black hole?
user avatar
1 vote
1 answer
159 views

Do black holes emit dark matter as Hawking radiation?

When a star made from protons neutrons and electrons becomes a black hole that black hole can emit protons neutrons and electrons as Hawking radiation. Dark matter is unusual matter: is there any ...
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