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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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Why do “they” portray colliding black holes like that?

When I see an animation of two colliding black holes anywhere, it looks like two merging beads of water. But why would the event horizon form a bridge during collision? There is no material flowing in-...
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Is there a better explanation of Hawking radiation?

I'm writing a piece on Hawking radiation, and find I have something of a problem. The "given" explanation which I find on Wikipedia and elsewhere is unsatisfactory: "Physical insight into the ...
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Can a black hole turn back into a star? [duplicate]

I understand that a black hole happens after a star exhaustions elements capable of undergoing fusion. Without the energy produced by fusion the remaining mass of the star collapses on itself and ...
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Does a magnet outside a black hole affect one inside it?

If I had 2 really strong magnets, and I threw one into a black hole, while holding one outisde it at a safe distance, what would happen? Would the magnets affect each other in any way? Would one push/...
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Black hole without singularity?

My question is about the equivalence about having an event horizon and having a singularity. In one side the implication looks pretty obvious: A singularity implies having an event horizon and ...
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Symmetry in Hawking radiation?

I have a question concerning how Hawking radiation works. As I understand, a pair of particle-antiparticle may pop to existence near the event horizon (from a virtual particle). Then it might happen ...
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As a black hole passes through spacetime, does it affect it?

Nothing in the universe stands still. It's always on its way from somewhere to somewhere. A black hole follows a trajectory through the universe, moving from one locus in spacetime to another locus. ...
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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 ...
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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 ...
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Why black holes have positive energy?

How could Hawking get the conclusion "[...] and black holes have positive energy. That’s why empty space is stable. Bodies such as stars or black holes cannot just appear out of nothing. But a whole ...
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How does the Gamma Ray Burst that occurred when 2 black holes merged compare to other GRB's?

A Gamma Ray Burst was detected 0.4 seconds after the gravitational wave event, GW150914, caused by a black hole merger, and it was in the same part of the sky. It is uncertain whether that Gamma Ray ...
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What effect does time dilation have on bodies orbiting close to Black Holes?

As far as my (somewhat basic) knowledge of astrophysics goes in general the closer to a star your orbit gets smaller (because you travel less distance) and faster (because you're deeper in the gravity ...
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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 ...
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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 ...
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Can matter fly directly into a black hole and avoid the accretion disc?

From what my non-scientifically-trained mind understands, matter typically enters a black hole via getting caught up in the accretion disc going faster and closer to the black hole until it passes the ...
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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?
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How can gravitational waves escape from the gravity of black hole?

I know that even light can't escape from a black hole's gravity and the velocity of light and gravitational waves are the same. How can only gravitational waves escape from its gravity?
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How can X-rays be emitted from a black hole? [duplicate]

A black hole's gravity prevents light from escaping, how can a black hole emit X-rays? Visible light and X-rays are both electromagnetic radiation, shouldn't the black hole's gravity prevent X-rays ...
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How the position of this black hole known?

How do scientists know the positions of black holes? Observe the highlighted area in the image:
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Does our current understanding of the mass of black hole only allow for it to be located at the singularity? [duplicate]

Does the distribution of mass or density of mass inside the event horizon matter for a black hole to exist as we currently theorize? Could the mass inside the event horizon be distributed in any way ...
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Neutrinos passing through black holes

What would happen to a neutrino that, traveling parallel to the black hole, crossed it's event horizon? Would it come through the other side unaffected? Or, A neutrino and a black hole just happen to ...
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Spaghettification of hard-things/Elements

Is it possible for a black-hole to easily stretch or turn any hard object like (Diamond , Gold bar , Platinum bar , Brass) into spaghettification state in just a seconds or minute once it gets near ...
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Could undiscovered smaller black holes within galaxies be an explanation for dark matter?

From what I've read, given the speed of stars rotating within a galaxy and the known mass, the stars' speed is too fast to stay in orbit. Dark matter was proposed to explain this but is it possible ...
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What can the average Astronomy Enthusiast do to learn more [closed]

Maybe this sounds like a silly question (and hopefully is legitimate), but I will elaborate a little more. I seem to love astronomy, every single thing about it, I find it brilliant, interesting, ...
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Relative black hole?

When some object is moving, it appears smaller and more massive. What if it's moving so fast it should become a black hole? Some calculations: Let observed radius $R_0\gamma$ ($R_0$ - radius at rest) ...
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Why is the statement “black holes make up 1% of the mass of the Milky Way Galaxy” unknown?

a) We cannot detect all black holes and therefore don't know the percentage of the galaxy's mass they make up. b) We do not know the mass of the Milky Way's central black hole. c) According to our ...
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Does black hole have the following properties? [closed]

Black holes emit x-rays lights from within their event horizons (I believe this one is unknown because you cannot see what's going on inside event horizon) A 9 km black hole may be hidden between ...
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Gravity of other objects in black holes?

If something falls into a black hole, but has not yet hit the singularity in the center, can we (outside of the black hole) feel its gravity? On the one hand, I've learned that there's no distance ...
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Can we resolve the centers of Milky way's satellite galaxies now?

Two dwarf satellite galaxies of our galaxy have large $\frac{\text{diameter}}{\text{distance}}$ values. And one of them, Canis Major Dwarf, is 8kpc away which is the same with our distance to the ...
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What would happen if a planet would acumulate mass continously?

If a star accretes enough mass it collapses into a black hole (I am not a physicist or an astronomer so I guess this is the simplified version). But what would happen if a forming planet continued to ...
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Are there upper or lower mass limits for black holes?

Natarajan & Treister (2008) describes a practical upper limit for black hole masses at $\sim 10^{10} M_\odot$. This is all due to the black hole's interactions with nearby matter. However, is ...
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Age of a black hole

Is there a way to determine the age of a black hole. Suppose 100 Billion years from now, if two black holes have exactly the same mass(say 30 M☉). One of them formed 10 Billion years from now and ...
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Fate of helium moving toward a singularity

On the molecular level, if an atom, consider helium, were to fall into a black hole, what would be the ultimate fate of its electrons, protons and neutrons?
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How could lithium burning take place in a quasi-star?

According to Begelman et al. (2008), one of the most distinguishing features of the hypothetical quasi-star is that it's supported by radiation pressure from the accretion disk of the black hole in ...
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Why Did The Universe Expand? [duplicate]

If all of the mass and energy in the universe was in a point smaller than the size of an electron at one time, why did it expand? Did it necessarily expand immediately on formation, or could it have ...
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Do black holes produce thermal radiation?

Do black holes produce thermal radiation, as expected on theoretical grounds? Does this radiation contain information about their inner structure, as suggested by gauge–gravity duality, or not, as ...
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Energy needed to create a black hole vs energy needed to run the Large Hadron Collider?

I was disappointed to hear Brian Cox's flippant reply to whether or not the LHC could create a black hole big enough to swallow the earth in this video: https://www.youtube.com/watch?v=QFy87tFTZwY I'...
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Black hole Creation

I just had an idea not sure if this would work but if we dropped something into very deep water like the marina trench could the pressure crush it small enough to create a black hole?
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Do black holes pull in and keep spacetime itself or merely warp it but ultimately let it pass through?

Forgive my 'amazing' MS-Paint skills, but this is along the lines of what i'm wondering: Is there any situation where Scenario A occurs, or is space always dragged back out as in Scenario B?
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Could the merger of two rotating black holes create another that breaks the rotational speed limit?

The black hole GRS 1915+105 was observed to be spinning at near the theoretical maximum spin rate. Assuming you had two such black holes spinning clockwise, and also orbiting each other clockwise, ...
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What is the speed of gravitational waves ? [duplicate]

I read that two huge black holes collided or merged and so it created gravitational waves billion years ago , So now we are able to detect it & detected it. So what is the speed of gravitational ...
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Does creation of galaxy depend on black holes?

I've read many times that every galaxy contains a black hole at the center. So is the creation of a galaxy linked to black holes?
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How does a black hole spin?

This seems like a pretty basic question, but I couldn't find a duplicate upon quick inspection. From what I understand about black holes they actually contain no matter. All of the mass that maintains ...
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Complex life in binary black hole - Sun(s) system

I was wondering if there could theoretically exist systems in which an Earth-like planet was in the habitable zone of one (or two) Sun-like star(s), while actually not orbiting around any star. To be ...
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Could information be transmitted from inside a black hole using gravitational waves?

Could you use gravitational waves to communicate from inside the event horizon of a black hole to someone who was outside?
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When are gravitational waves emitted during a merger of black holes?

When black holes are merging, and emitting gravitational waves, are we seeing those waves start when the event horizons are merging, or when the singularities are merging?
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Is there mass i.e a physical bottom to a black hole? [duplicate]

All matter has a gravitational pull, a ball, a rock, a planet and a star - the bigger the matter the more it affects the space fabric around it thus having a greater gravitational pull. I see black ...
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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 ...
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Succinct explanation of black hole mass, diameter, shape?

I don't have any formal education in physics and I have found it hard to find a succinct and somewhat simple to comprehend explanation of what we think is the actual reality of a black hole. I'm ...
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Can we discern black holes with visible light?

Sorry for my dumb terms. I'm interrested in astronomy but I have next to zero background. Given that a black hole absorbs everything, including light, could we ever discern one with visible light (...