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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59
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5answers
12k views

Why not take a picture of a closer black hole?

There are closer galaxies than Messier 87 for sure, even ours! It sparked my curiosity that they went with one 53 million light years away. Is there a reason for this?
59
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2answers
8k views

Can gravitational waves pass through a black hole?

As the title says, what happens when a gravitational wave approaches a black hole? I would presume that something interesting happens because of the way spacetime works near black holes but I have no ...
53
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2answers
11k views

If two black hole event horizons overlap (touch) can they ever separate again?

Hypothetical question based on my understanding that two event horizons that overlap (touch) can't ever separate again: Imagine a 1 billion solar mass black hole (so the event horizon is massive and ...
42
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11answers
17k views

Why do Black Holes in the middle of galaxies not suck up the whole galaxy?

As stated in several sources, it's supposed that in every galaxy there is a black hole in the middle. My question is, why do these black holes in the middle of galaxies not suck up all the ...
39
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5answers
8k views

Why does gas form a star instead of a black hole?

When a space gas gets pulled together a star is formed. On the other hand, when a massive star dies, it collapses to a black hole. You would think that the initial mass of the gas would be bigger ...
38
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5answers
2k views

How are black holes found?

Black holes have so much gravity that even light can't escape from them. If we can't see them, and the suck up all electromagnetic radiation, then how can we find them?
36
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5answers
5k views

How do we know that black holes are spinning?

How is it possible to know if a black hole is spinning or not? If a planet is spinning, you can see it clearly but you can't really see a black hole. Next thing would be that matter interacts with ...
36
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3answers
7k views

Why are there uneven bright areas in this photo of black hole?

In the recently released photo of a black hole shown above, which was created by using data from EHT, why is the lower region brighter than the one above? Is it because of the rotation of the ...
35
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2answers
35k views

How does neutron star collapse into black hole?

We know the spectacular explosions of supernovae, that when heavy enough, form black holes. The explosive emission of both electromagnetic radiation and massive amounts of matter is clearly observable ...
34
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7answers
5k views

Does matter accumulate just outside the event horizon of a black hole?

My understanding is that time slows and approaches stopping when approaching the event horizon of a black hole. I have seen this explained several places, including a brief explanation in the last ...
33
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5answers
5k views

How exactly does Hawking radiation decrease the mass of black holes?

From what I understand so far, when one of virtual particles crosses the event horizon and the other does not, they can not annihilate each other. The latter wanders off into the universe (btw, is it ...
32
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6answers
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What did LIGO Actually See? (Gravitational waves discovery)

I am trying to find an original video/image of what LIGO actually saw, but all I can find is artist renditions of gravitational waves.
31
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2answers
11k views

Can our Sun become a black hole

Does every star become a black hole? Is there any probability that our sun can become a black hole? If yes then is it on its way to become a black hole? what is the current state of sun as per the ...
30
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2answers
6k views

Are black holes spherical during merger?

I've been thinking about black holes, specifically during the final moments before two merge. I'm wondering if black holes, or I guess more specifically their event horizons, are always spherical. ...
26
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6answers
3k views

Can we (theoretically) spin the black hole so strong that it will be broken apart by centrifugal force?

I can't imagine the forces involved in black holes' lives. So please, help me to find out, if it is possible or not to destroy black hole in this specific way.
25
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2answers
7k views

Why didn't the Event Horizon Telescope team mention Sagittarius A*?

At the press conference this morning, the Event Horizon Telescope team didn't say much about Sagittarius A*, which was the target many of us have been waiting for. Is there any explanation anywhere ...
25
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3answers
4k views

Why can't light escape from a black hole?

I've heard that light can't escape from a black hole. Can it? If not, why?
24
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4answers
7k views

What are the differences between a Black Hole and a Supermassive Black Hole

From what I understand, the mass of a black hole should be nearly infinite, how much more massive can something get? Is the name to be literally interpreted such that a Supermassive Black Hole just ...
23
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5answers
6k views

Why did the big bang not just produce a big black hole?

Questions I've often wondered about: 1) If all the matter and energy were concentrated at a single point at the big bang, why wasn't that a black hole, or why didn't it form one? 2) If the reason #1 ...
20
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3answers
6k views

Speed of light in a black hole

If I had a directional photon-emitting source and placed it inside a black hole pointing upward and out towards the visible universe, I assume the photons traveling at the speed of light would slow ...
19
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3answers
3k views

What is a singularity? What is at the center of a black hole? Specifically regarding space-time

So because I can only really think of space-time in 2-dimensions like a sheet of something, my assumptions might be wrong to begin with. I was watching a YouTube video on black-holes and there was a ...
19
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2answers
2k views

Explosions of black holes

I was bopping around YouTube and observed this enjoyably produced video. In it, when describing the behavior of a black hole with the mass of a US nickel, the narrator says, "Its 5 grams of mass will ...
18
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3answers
2k views

Escaping a black hole

I often hear that nothing can escape a black hole because it's "escape velocity" is greater than c. If that is accurate, what about the following. I know that the following has a lot of most likely ...
16
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5answers
8k views

If all stars rotate, why was there a theory developed that requires non-rotating stars?

According to Penrose's research, a non-rotating star would end up, after gravitational collapse, as a perfectly spherical black hole. However, every star in the universe has some kind of angular ...
16
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3answers
750 views

Could there be dark matter black holes?

Could dark matter compress and form black holes? Since dark matter is even more abundant than normal matter, a dark matter black hole should not be rare...right?
16
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3answers
3k views

How can a supermassive black hole cause so much energy to enlighten its matter when its massive gravity prevents light to escape?

To cite the German newpaper article Astronomen beobachten erwachendes Schwarzes Loch: Das Materie-Monster sitzt den Angaben zufolge im Herzen der 42 Millionen Lichtjahre entfernten Polarring-...
16
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3answers
722 views

Dimensions of a black hole

How big can a black hole become and how small can a black hole become?(minimum and maximum dimensions of a black hole)
16
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1answer
2k views

Has Hawking Radiation Ever Been Observed?

I know Hawking Radiation has firm theoretical footing, but has a signal ever actually been observed? What observational research is being done to attempt to see this effect? Is it simply too tall an ...
16
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2answers
885 views

What are practical considerations for backyard radio-astronomy detection of black holes?

Evidently, direct observation of a black hole for an amateur astronomer, such as described for what professionals do in the question "How are black holes found?" would be nigh on impossible, so the ...
15
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4answers
604 views

Why do Earth and moon move apart but binary black holes move closer?

According to the accepted answer on Is the moon moving further away from Earth and closer to the Sun? Why?, the moon is receding from Earth because tidal forces and friction cause energy to be lost. ...
15
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3answers
7k views

Maximum spin rate of a black hole?

I have just been watching a podcast called "Deep Astronomy" and the discussion was about a super fast spinning black hole discovered with the NuSTAR space observatory. This black hole was modeled with ...
15
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6answers
3k views

Is it possible that some stars are already black holes yet we see light emitted from before becoming a black hole?

For stars we see that are burning fuel at a fast rate, that are very bright, (or any star for that matter sufficiently far away from us) could it be that they are already black holes (the sufficiently ...
15
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4answers
5k views

Black Hole / Hawking Radiation: Why only capture anti-particle?

I may have some specifics wrong here. If so, don't focus on those. Just focus on the general thrust of my question. I "understand" (cough) that particle/anti-particle pairs form spontaneously in ...
15
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3answers
2k views

Infalling observer could never cross Black Hole event horizon? [duplicate]

I have an interest in cosmology, but I would no way consider myself an expert. It would be great if the more knowledgeable contributors would be able to answer the question I have posed. The intense ...
15
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2answers
1k views

Would a black hole evaporate via Hawking radiation before you fall past the event horizon?

It takes an infinite amount of time for something to fall past the event horizon of a black hole from the perspective of someone outside the event horizon. Black holes also evaporate after a finite ...
14
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4answers
302 views

Are there ways other than the collapse of a star which have been observed to form black holes?

Every time I hear about a black hole, it's always in conjunction with the collapse of a star. Have any other processes been observed to create a black hole?
14
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5answers
393 views

Orbiting around a black hole

Is it possible (for either a satellite or a planet) to orbit around a black hole? Do they attract everything around themselves into the center? Or they just affect gravitational force just like stars?
14
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1answer
2k views

Why can't supermassive black holes merge? (or can they?)

The CNet article Astronomers discover two supermassive black holes in a death spiral links to Discovery of a Close-separation Binary Quasar at the Heart of a z ~ 0.2 Merging Galaxy and Its ...
14
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1answer
433 views

Can any information leave a black hole?

Referring to this question, is there any information that can leave black holes? Are they causing a permanent information loss in our universe?
14
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1answer
674 views

Will an observer falling into a black hole be able to witness any future events in the universe outside the black hole? [duplicate]

I know someone or something sucked into a black hole could not survive, but is the bending of light so immense that an observer falling into a black hole will be able to witness any future events in ...
13
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3answers
916 views

If nothing travels at the speed of light, except light, how can a black hole also pull light into itself?

Is it because it has super massive gravity and energy? Or is it some sort of an anti-light component in it because it used to be a star?
13
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3answers
887 views

Statistically, what would the average distance of the closest black hole be?

The closest confirmed black hole is several thousand light years away from earth. Our galaxy has about 100 billion stars. I didn't find any reliable information on the black hole count of ratio versus ...
13
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1answer
963 views

Does blackhole merging break their event horizon segregation?

So far as I know, if we have 2 blackholes A and B, both having their own event horizons, then what's inside the event horizon of A remains completely unknown to us, and same for what's inside the ...
13
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1answer
644 views

Is it safer to be near a star or a black hole?

If a star or black hole neared the solar system, which would do the least damage? For the sake of a good comparison, lets assume the candidate star is an "average" 5 solar mass star, and the black ...
13
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1answer
256 views

Which came first: black holes or galaxies?

In other terms, did galaxies grow around black holes at their center?
12
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3answers
3k views

Can I make a black hole with one or two atoms?

So I was watching something that said if we compressed Earth into the size of a peanut: we would get a black hole; if we compressed Mount Everest into a few nano-meters; we would get a black ...
12
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3answers
3k views

Is there a maximum size for a black hole?

As far as I understand it black holes radiate Hawking radiation and probably gravity waves, which over time causes them to lose mass and eventually evaporate after almost unfathomable amounts of time. ...
12
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2answers
3k views

As matter approaches a black hole, does it speed up?

If so, how do we know it speeds up? Doesn't time slow down as gravity increases? If time slows down around a black hole, is it possible matter doesn't actually speed up?
12
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2answers
3k views

Do all galaxies have a black hole in the center?

Would I be correct if I stated that all galaxies have a black hole in the center? Since other galaxies orbit around a center point in a galaxy - the barycenter, right? - I would assume at this point ...
12
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2answers
238 views

Are black holes expected to contain the same ratio of dark matter to regular matter as the rest of the universe?

Are black holes expected to contain the same ratio of dark matter to regular matter as the rest of the universe? I've heard that dark matter is distributed in halos around galaxies. Does that make it ...