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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black Holes and Neutron Stars

if the universe is constantly expanding then the distance between black holes and neutron stars must be increasing. Then What makes them to come under the influence of each other's gravitational ...
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How does a supernova occur when a massive star collapses into a black hole?

My layman's understanding of a supernova explosion is that it's caused by a rebound when a massive star collapses. When the core collapses to a point where neutron degeneracy pressure dominates, the ...
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How fast does a spacecraft have to be to enter a primordial black hole without being torn apart?

If there really is a primordial black hole beyond the Kuiper belt, we can send a probe to the black hole and into it. But how fast must the probe be in order to enter the black hole without being ...
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Can the WISE telescope detect black holes?

Black holes are hot, aren't they? With its infrared scan, could the WISE telescope also detect a black hole? The hypothetical planet beyond the Kuiper belt could actually be a primordial black hole. ...
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Have we ever seen the formation of a blackhole?

So I know that the formation of a supernova has been observed and that we have taken images of blackholes, however, has the formation of a blackhole ever been observed. How do we observe it?
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Jet streams of black holes emit [duplicate]

The speed of light is the upper limit at which conventional matter can travel. However, jet streams propel "material (...) at a significant fraction of the speed of light" (Wikipedia). Let me ...
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What happens with the black hole's mass when a black hole disappears?

If a black hole isn't "fed" by attracted matter, it disappears someday. But how is that even possible? What happens with the mass at its singularity? It can't just disappear or am I wrong with ...
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What observational data convinced Stephen Hawking that Cygnus X-1 was indeed a black hole and caused him to break into Kip Thorne's office?

It's generally easier to be certain an object is a star than a black hole. HDE 226868 is one of our site moderators and a blue supergiant star. The latter has a 5.6 day companion that supplied a ...
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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'...
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Can a black hole with the density of water exist?

During an outreach event, the speaker mentioned the fact that black holes weren't necessarily dense objects and that black holes of any density could exist, even black holes with the density of water. ...
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Why are pseudo-Newtonian potentials used to model accretion disks around Schwarzschild black holes?

The general relativistic effective potential in Schwarzschild geometry (in units $G=M=c=1$) is expressed as $$V_{eff}=\sqrt{\left(1-\frac{2}{r}\right)\left(1+\frac{l^2}{r^2}\right)}$$ where $r$ is the ...
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Why does Newtonian physics give the right radius for a black hole?

When computing the distance at which the escape velocity is equal to the speed of light, the result is equal to the Schwarzschild radius. Is this just a coincidence, or is there a physical reason why ...
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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?
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Primordial black holes microlensing

Could the movement of a PBH found in the outer solar system by microlensing be totally unpredictable and impossible to track after it was first detected?
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Does a black hole necessarily contain a singularity?

I'm basing this hypothesis on the theories around how an outside observer watching something fall into a black hole will never actually see the thing pass the event horizon. And secondly that from the ...
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How can a singularity actually exist?

Probably a stupid question, but it "bothers" me and I can't find a concrete answer on the internets. When you fall into a black hole, afaik, time slows down for the matter falling in as it gets ...
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What is a thermal distribution of eccentricities?

The abstract of the new (open access) paper in Nature A statistical solution to the chaotic, non-hierarchical three-body problem says: The three-body problem is arguably the oldest open question in ...
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What is the temperature of the black hole?

Are black holes hot or cold? I was thinking because I wanted to know if there any human sustainable temperature so we can travel in it.
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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 ...
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Why would a black hole have a disk, but not emit x-rays?

There's a recent paper in Nature about LB-1, a B-class star orbiting a massive black hole. I don't understand how these two parts of the paper can be reconciled. On page 2, the authors argue that the ...
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If we accelerate a neutron star to move at speeds comparable to light would it become a blackhole because of the added energy?

Could a neutron star turn into a blackhole if it is accelerated to near luminal velocities? And if it slows down after a while, does it become a neutron star again?
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Black hole collision animation: What are these extrusions?

In this video uploaded by LIGO Lab Caltech, two inspiraling black holes are depicted. The video's description explains what is shown and can be summarized by: The colored surface is the space of ...
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How much starlight do black holes absorb?

Can it be calculated how much light from other stars a black hole of certain sizes would absorb? And how long will it take for the number of active stars to decrease to the point where Hawking ...
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Could S5-HVS1 conceivably still hold on to any planets?

If the star (S5-HVS1) has been accelerated to 1,700 km/s by a close encounter with the super massive black hole at the centre of our galaxy (Sagittarius A*) what would happen to any planets orbiting ...
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Could a star closely orbit a black hole long enough for the star to have lost 0.5B+ years to time dilation?

I was wondering how stable a close star-black hole system could plausibly be, and thus how much time a star could plausibly miss out on (from an outside observer's perspective) due to being in an ...
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Whats the time dilation difference between the earths reference and (near) the milky way galaxy central black hole? [duplicate]

How much difference in time is there between our time of reference and very near the black hole at the center of our galaxy. I was trying to get answer in terms of something like "1 year in here ...
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Can primordial black holes be found orbiting other stars?

A recent study suggests a that a primordial black hole may be orbiting the sun at and that they can be common near other star systems. What measurements and equipment can perhaps find BH's near ...
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How much damage would collision with a similar mass primordial black hole do to earth?

All this talk of Planet 9 perhaps being a primordial black hole (PBH) made me wonder how dangerous a PBH collision with earth would really be. Specifically, if earth collided with a PBH of 1 earth ...
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In what ways can force be applied to a black hole

Besides gravity I have never heard of another force pushing or pulling a black hole. Does an object falling into a black hole push the black hole when it crosses the event horizon? What happens to the ...
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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 ...
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Black holes exhaustion

Can accelerating black holes radiate their mass as an gravitational wave?If that is true maybe dark matter is not something but it is just gravitational waves from an exhausted dense object.
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A question related to black holes

Not a physicist just a simple guy, don't know much about physics as well. Just like to read things. I was reading about black holes and a question popped in my mind. If I understand it correctly ...
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Does the spin rate of a black hole correspond to a physical feature?

If the mass and orbital period for two neutron stars is known before collapse to a black hole and the rate of spin is known after collapse, 100 revolutions per second for instance, that will correlate ...
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What is a black hole's “shadow” and the best angle to view it to measure the spin?

This excellent answer mentions several ways to try to observationally measure the spin of a rotating black hole. The third one is intriguing, but I don't understand how this works: The spin of a ...
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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 ...
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Why does the outside edge of a Kerr black hole ergosphere rotate at the same speed as the inner edge?

Reading through the Wikipedia on a Kerr black hole ergosphere, and this nice question on the maximal spin rate of a black hole leads me to ask: why does the outer edge of the ergosphere rotate at the ...
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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 ...
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Is there a way to calculate how much damage black hole merger shockwaves inflict on nearby objects?

Black hole mergers lose respective rotational energy during a merger. I understand that the energy 'emitted' is scattered as gravitational 'energy' that can henceforth be detected by gravitational ...
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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 ...
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Could anyone recommend a good book about the basics of astrophysics? [closed]

I am sorry if a similar question has been asked before. I look at other questions but was not entirely satisfied. So, I am a Psychology student who would like to know more about the basics of ...
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Control the behavior of a Black Hole

Is it possible to manipulate the size of a black hole or how a black hole behaves if scientists were able to synthesize hawking radiation on demand. That is, if I could find a way to imitate hawking ...
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How does a Super-Massive Black Hole 'flare'?

This week we have read of evidence of the Super Massive Black Hole in the centre of the Galaxy 'flaring'. My understanding is that light cannot escape from a black hole. My question is: How does a ...
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Origins and most frequently used; perinigricon vs peribothron?

Gizmodo.com's Astronomers Spot Unprecedented Flashes From Our Galaxy's Black Hole mentions Sgr A*'s companion gas cloud G2 and that Wikipedia article uses the term perinigricon, but that mentions ...
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Could anything consume a small black hole?

Whenever I read about black holes, it is normally involving how they devour anything that comes too close... regardless of how big anything is. But what if it were a really small black hole vs ...
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Black hole's gravity

Is gravity relative to volume, or size of an object? Since a black hole is a massive star that collapses on its weight, how comes the same sun's mass, when it becomes a black hole, provides gravity ...
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What would happen to black holes during the Big Rip?

If the universe expands fast enough to rip atoms apart, what will happen to black holes? Would they rip apart too? What would that be like? Would they expand along with the universe's expansion, or ...
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Can a black hole formation be stopped or interrupted

My question is a hypothetical: if I were to create a black hole the size of a family house, in New York, is there any way that it can be stopped, or interrupted? If a black hole of this size is formed,...
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Could the rotation of a black hole cause other planets to rotate?

Because everything rotates so perfectly, and we know that some blackholes rotate and they're the biggest things in the universe, so a silly question comes to mind. If you remove all black holes from ...
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Two body orbit dynamics for orbital periods approaching light cone limit

How do you model a system of two large celestial bodies, where they achieve a rotation very close to the limit at which information can escape the system (heat, light, etc.), do they begin to appear ...
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Why does matter spiral into blackholes?

Narrators of astrophysics documentaries constantly state that matter spirals into black holes as if it were intuitive that this would happen because of gravity. But the moon isn't spiralling into the ...

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