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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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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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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
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
5 votes
2 answers
748 views

How does the Event Horizon Telescope implement the interferometry?

The BBC article Event Horizon Telescope ready to image black hole describes the Event Horizon Telescope, a coordinated observing technique with several radio telescope arrays across the globe forming ...
uhoh's user avatar
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5 votes
2 answers
2k views

Is our universe included inside a black hole? [duplicate]

This question repetitively comes to my mind but I've never found any good scientist article to argue about it, only esoteric or speculative web articles without much valuable background. So let's ...
CitizenInsane's user avatar
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
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
15 votes
3 answers
13k views

Would time go by infinitely fast when crossing the event horizon of a black hole?

If you were to fall into a black hole, my understanding is that from your reference point, time would speed up (looking out to the rest of the universe), approaching infinity when approaching the ...
Jonathan's user avatar
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14 votes
2 answers
2k views

Is it possible that a ultra-large portion of the space we live in is already inside a black hole? How could we refute this?

Trying to wrap my head around some concepts involving the very large gravitational fields of black holes, and what the gravitational gradients look like on a cosmic scale. I'm familiar with the Great ...
Ian Moriarty's user avatar
5 votes
1 answer
1k views

Parent stars of our Sun - Where are its remains?

This is in a way related to this question. Question is: Our star is third generation star, which is explained by existing Barium. That Barium was created by other stars. Now, those stars must have ...
Amiga500's user avatar
  • 203
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
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
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
16 votes
3 answers
2k 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 ...
this's user avatar
  • 437
16 votes
4 answers
2k views

M87 Black hole. Why can we see the blackness?

So, as the title states, why are we able to actually see the 'blackness' of the black hole? I get that what we are actually seeing is the event horizon, or accretion disk. But should this not extend ...
MCG's user avatar
  • 805
7 votes
1 answer
602 views

Collision of 2 black holes

There is a large number of visible Supernovas. Each week - about a 20 Supernovas Type 1a around the Universe. Is there collisions of Black Holes? What is this collision called? E.g. 2 black holes ...
user1346's user avatar
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
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
16 votes
4 answers
679 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?
Zoltán Schmidt's user avatar
13 votes
2 answers
7k 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 ...
FutureCake's user avatar
13 votes
2 answers
7k views

Observable universe equals its Schwarzschild radius (event horizon)?

The estimated age of the universe is 14 billion years. The estimated Schwarzschild radius (event horizon) of the observable universe is 14 billion light-years. What are the ramifications?
Dirk Helgemo's user avatar
11 votes
2 answers
2k views

Why do black holes have jets and accretion disks?

If supermassive black holes possess the gravity required to prevent the escape of photons and other mass particles, why do jets and accretion disks form? They seem to indicate that something is ...
Naftuli Kay's user avatar
8 votes
1 answer
897 views

What defines the plane of an accretion disk around a black hole?

The question Do we know at which angle the Event Horizon Telescope will look at the accretion disk of Sagittarius A*? about just how close to edge-on we would be viewing any accretion disk around the ...
uhoh's user avatar
  • 30.8k
7 votes
2 answers
1k views

What part of the EM spectrum was used in the black hole image?

The EHT has published the first image of a black hole. It is the event horizon of the singularity in M87 against its accretion disk. I've been through the reports in the popular press but none ...
Dave Gremlin's user avatar
  • 1,071
4 votes
2 answers
440 views

What is the "hypothesized lower mass gap" between 2.5 and 5 solar masses?

Searching here for "mass gap" yields nothing yet. Penn State's Black hole or neutron star? LIGO-Virgo scientists find mystery object in 'mass gap' begins: When the most massive stars die, ...
uhoh's user avatar
  • 30.8k
4 votes
1 answer
873 views

Could Planet Nine be a tiny black hole or an exotic compact object such that it escaped detection? What would its bounds be?

Planet Nine (a variant of the old X-Planet and Tyche-Thelistos hypothesis) proposes a super-earth planet at the edges of the solar system with a mass of around ten Earths. However, given the interest ...
riemannium's user avatar
3 votes
1 answer
683 views

Size of a black hole

If there is no matter inside any of the black holes and all of them have a singularity in the center of them, which is infinitely small and infinitely dense, then how can they differ in size and ...
Ba-Lee's user avatar
  • 41
2 votes
1 answer
495 views

What can be learned from, or noted in this LIGO Orrery video?

The Ars Technica article Physicists detected gravitational waves from four new black-hole mergers notes that This brings the total number of events detected by LIGO and Virgo to 11. It also has a ...
uhoh's user avatar
  • 30.8k
2 votes
1 answer
1k views

Do black hole singularities actually merge?

new questioner here so please be gentle. Do the singularities of merging black holes actually merge together? I mean there are 2 infinitely small objects (singularities) that are trying to find each ...
Coyote62901's user avatar
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
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
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
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
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
  • 30.8k
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
15 votes
4 answers
1k 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. ...
Gnubie's user avatar
  • 663
13 votes
4 answers
4k views

Do Roche limits apply to black holes?

Consider black hole A, a super massive black hole at the center of the galaxy. Orbiting it is black hole B, a much less massive black hole. If some passing body were to modify black hole B's orbit ...
Sidney's user avatar
  • 567
13 votes
2 answers
1k views

Mass of black holes compared to parent star

What is the range of percentage mass of parent star left in a stellar black hole directly after its formation? What factors determine this number for a specific case?
Frank J's user avatar
  • 133
12 votes
3 answers
1k views

Why can't a quasistar exist now?

From my research, I found out that quasistars theoretically existed because of a black hole core whose radiation pressure counteracted gravity within the star. However, a few websites stated that ...
Pyrania's user avatar
  • 290
11 votes
1 answer
799 views

How far away is the nearest compact star remnant likely to be?

Neutron stars and black holes are hard to detect when they are solitary, and there seems to be big uncertainties about how common they are. White dwarfs are much easier to detect and the nearest one ...
LocalFluff's user avatar
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10 votes
5 answers
9k views

Can things move faster than light inside the event horizon of a black hole?

Black Holes are regions of space where things get weird [Citation Needed]. Past the event horizon of a black hole, any moving particle instantaneously experiences a gravitational acceleration towards ...
Sidney's user avatar
  • 567
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
  • 30.8k
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
9 votes
1 answer
430 views

Why doesn't the black hole in the center of the Milky Way glow similarly to the famous M87 image?

The M87 image made some astronomers famous recently as the first image of a black hole. In the Milky Way, it has been concluded that there must be a black hole due to the movement of stars near the ...
user985366's user avatar
8 votes
3 answers
1k views

Why does the Event Horizon Telescope (EHT) not include telescopes from Africa, Asia or Australia?

The Event Horizon Telescope seems to include these radio telescopes currently: Image by European Southern Observatory (ESO)/O. Furtak; CC-BY 4.0-licensed, see the source on Wikipedia Commons and the ...
rugk's user avatar
  • 183
7 votes
2 answers
6k views

Does a black hole become a normal star again?

Stars which exceed the Tolman-Oppenheimer-Volkoff limit can become a black hole. What happens to star after it becomes a black hole? Does it regain its status of star?
Strikers's user avatar
  • 1,109
6 votes
2 answers
258 views

How would a small nearby black hole be detected and confirmed as such?

This article suggests that there might be a tennis ball-sized black hole orbiting the Sun somewhere beyond the orbit of Neptune. According to the article, observational anomalies of trans-Neptunian ...
Anthony X's user avatar
  • 783
5 votes
2 answers
1k views

GW190521 black hole merger total mass calculation and missing mass, how does this happen?

I have just read an article about that black hole merge event (it's in Italian): Sette miliardi di anni fa, due mostri si unirono What made me curious is that the article tell that a 66 solar mass ...
Skary's user avatar
  • 173
5 votes
4 answers
1k views

How does gravity have an effect from the inside the event horizon of a black hole with the rest of the universe?

According to general relativity, as I understand it, the space around a black hole's event horizon is distorted by gravity, such that the distance to a point approaching the event horizon from an ...
Robert Mashlan's user avatar

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