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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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77 votes
2 answers
11k 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 ...
dalearn's user avatar
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75 votes
5 answers
15k 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?
Morgan's user avatar
  • 733
67 votes
2 answers
14k 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 ...
Loadwick's user avatar
  • 691
55 votes
9 answers
11k 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 ...
Jonathan's user avatar
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49 votes
11 answers
21k 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 ...
OiRc's user avatar
  • 613
45 votes
5 answers
6k 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 ...
sirzento's user avatar
  • 645
45 votes
2 answers
49k views

How does a neutron star collapse into a black hole?

We know the spectacular explosions of supernovae, that when massive enough, form black holes. The explosive emission of both electromagnetic radiation and massive amounts of matter is clearly ...
SF.'s user avatar
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43 votes
5 answers
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 ...
Antons Voitov's user avatar
41 votes
5 answers
3k 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?
user avatar
41 votes
3 answers
9k 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 ...
Kushal Bhuyan's user avatar
38 votes
5 answers
7k 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 ...
marko-36's user avatar
  • 621
37 votes
2 answers
7k 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. ...
Ryan_L's user avatar
  • 643
37 votes
5 answers
16k views

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

Questions I've often wondered about: 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? If the reason #1 above ...
yadda's user avatar
  • 567
36 votes
7 answers
7k views

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.
Scott Taylor's user avatar
32 votes
3 answers
14k 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 ...
Strikers's user avatar
  • 1,109
29 votes
2 answers
4k views

Why does the 70-solar-mass black hole in the LB-1 system challenge current astrophysics?

Recently scientists discovered a large stellar-mass black hole, which (previously) they believed that it shouldn't be possible in our galaxy! Source An international team of scientists say they ...
Junaid S.'s user avatar
  • 391
27 votes
2 answers
8k 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 ...
White Prime's user avatar
27 votes
6 answers
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.
Pavel Voronin's user avatar
25 votes
4 answers
13k 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 ...
David Freitag's user avatar
25 votes
3 answers
6k 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?
user avatar
25 votes
3 answers
3k 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 ...
Thomas's user avatar
  • 381
24 votes
4 answers
5k 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 ...
gigatexal's user avatar
  • 503
24 votes
3 answers
14k 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 ...
Jack R. Woods'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 ...
user avatar
23 votes
4 answers
9k 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 ...
user3355020's user avatar
22 votes
5 answers
4k views

How far away are the events that caused the gravitational waves that have been detected?

A certain number of gravitational wave events have been detected. Is it possible to know how far away the mergers that caused those gravitational wave events are?
usernumber's user avatar
  • 17.6k
22 votes
3 answers
3k views

Escaping a black hole

I often hear that nothing can escape a black hole because its "escape velocity" is greater than c. If that is accurate, what about the following? I know that the following has a lot of most ...
Mitchell Kaplan'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
20 votes
2 answers
4k views

Is the center of our galaxy, the Sagittarius A* black hole a former star?

If a black hole comes from a dying star, do we have a record or proof that our galactic center was once a huge ball of burning plasma? I'm not an astronomy student.
TheRobloxGamer's user avatar
20 votes
4 answers
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-Galaxie ...
uuu's user avatar
  • 311
20 votes
3 answers
7k 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 ...
tnt-rox's user avatar
  • 355
20 votes
3 answers
1k 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?
Sir Cumference's user avatar
20 votes
2 answers
2k views

Is S2 still the fastest known star in the galaxy?

Wikipedia's entry for the star S2 says that it has the fastest known ballistic orbit, reaching speeds exceeding 5,000 km/s (11,000,000 mph, or ​1⁄60 the speed of light) and acceleration of about 1.5 ...
Connor Garcia's user avatar
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20 votes
2 answers
2k views

Is there an upper limit on the mass of black hole mergers we can detect?

From the LIGO website, black hole mergers have been observed between black holes with a mass up to roughly 50 $M_\odot$. Are there no black holes with a mass above 100 $M_\odot$ or is this an ...
usernumber's user avatar
  • 17.6k
20 votes
3 answers
5k views

Do Schwarzschild black holes exist in reality?

Do Schwarzschild black holes exist in reality? I have searched answer for this question but am not fully satisfied. Everything in the universe, including planets, stars, and galaxies, is spinning. How ...
apk's user avatar
  • 949
20 votes
1 answer
3k 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 ...
uhoh's user avatar
  • 31.1k
20 votes
2 answers
3k 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 ...
pdm's user avatar
  • 311
19 votes
4 answers
6k views

Can Newton's gravity equation explain why black holes are so strong?

I was just wondering why black hole's gravitational forces are so powerful. I know it's usually explained by Einstein's relativity which states that when an object becomes infinitely dense (a compact ...
AdiBak's user avatar
  • 655
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
  • 299
18 votes
5 answers
9k 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 ...
Murg's user avatar
  • 937
18 votes
4 answers
438 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?
user avatar
18 votes
1 answer
2k views

Are Buckyball-sized black holes possible?

The first item is the basic question; the subsequent items build upon it if it's possible. If these need to be broken into separate questions, I can do that, but they're pretty tightly related. Is a ...
RoUS's user avatar
  • 283
18 votes
1 answer
481 views

Which came first: black holes or galaxies?

In other terms, did galaxies grow around black holes at their center?
Kyriakos Kyritsis's user avatar
18 votes
2 answers
1k 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 ...
user avatar
17 votes
4 answers
5k views

If the Sun was replaced with a sun-mass black hole, would it be visually detectable?

Assuming it had no accretion disk, could we still detect e.g. distortions of the background star field?
2080's user avatar
  • 1,890
17 votes
2 answers
4k views

Why don't they make an image of the black hole in the M33 galaxy?

Since we see the Triangulum galaxy M33 from a quite vertical position (contrary to our Milky Way and a bit the Andromeda galaxy) it should be easy to image the black hole in the center of it, shouldn'...
user30007's user avatar
  • 1,236
17 votes
4 answers
10k 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. ...
Mark Rogers's user avatar
17 votes
3 answers
1k 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)
M.Tarun's user avatar
  • 953
17 votes
1 answer
3k 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 ...
astromax's user avatar
  • 5,953
16 votes
3 answers
6k views

Does General Relativity really predict Black Holes?

I'm doing some research on black holes for a science video contest. I want to explain the physics of how they work, but also want to have a little background on how they're formed. As far as I've ...
AdiBak's user avatar
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