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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1answer
437 views

Why smaller black holes are considered to be more dangerous than bigger black holes?

More massive the body is more is the gravity.Still often smaller black holes are considered to be very dangerous than the bigger ones,why?
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What does a black hole elements consists of

what are the elements of a black hole it just says what a black hole is? there must be elements that the sun consists of right?
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Physical measurements and celerity of black hole mergers?

LIGO detected a black hole merger for bh's of about 30 solar masses, with a schwartzchild radii of about 20km. Were the gravity waves generated by masses distanced by a few microns or a few ...
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Would LIGO Detect Head-On Collision?

Assume two black holes collide head-on. In other words, they were not orbiting one another before the collision. I know this is unlikely. Further assume that their sizes and distance from Earth are ...
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Why do neutron stars collide instead of just revolving around each other like planets revolve around the Sun?

We know about events like two neutron star colliding and resulting in a black hole, also collision of black holes, and collision of galaxies. But we never see a satellite such as a moon colliding with ...
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What will happen to the shape of a galaxy when a super massive black hole lying in its center dies(evaporates out)?

What's at the Center of the Milky Way? In this article it is said that a supermassive black hole lies in the center of milky way galaxy. At its center, surrounded by 200-400 billion stars and ...
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Why black holes are extremely cold?

"The most massive black holes in the Universe, the supermassive black holes with millions of times the math [sic] of the Sun will have a temperature of 1.4 x $10^{-14}$ Kelvin. That's low. Almost ...
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When black holes forms out of a supernova do they have a very high velocity?

When black holes forms out of a supernova do they have a very high velocity ?? Or do they remains at the position of parent star ??
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Is star a necessary phase in black hole lifecycle?

It now seems general fact that when a massive star core collapses at the end of its lifecycle it forms a black hole, can a black hole be formed skipping the star phase altogether?
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Can a black hole undergo a Penrose process inside another black hole's ergosphere?

I recently watched this video on black holes: https://www.youtube.com/watch?v=ulCdoCfw-bY And that statement should give you an idea of my level of understanding :) I was wondering if a spinning ...
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Black Hole growth [duplicate]

The latest info on black holes with regard to their formation is that since space and time go to infinity at the event horizon, from an outside perspective nothing ever enters a black hole, and it ...
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Star formation around rotating black holes?

Please excuse an amateur question. While trying to think of anything but what was happening during a dental procedure my mind turned to a model of a star close to a rotating black hole and the ...
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Is there a possibility that a white dwarf can turn into a neutron star or a black hole?

I know that a white dwarf is mainly balanced by electron degeneracy pressure and that if it gains more than 1.4 solar masses from any source (such as a companion star or a collision), it explodes as a ...
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Information Paradox with Hawking's Radiation

A theory about Blackholes storing the information from the universe. Being said that Blackholes are condensed mass sufficient enough to break every particle into different elementary particles, ...
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Are black holes different sizes thanks to the different sized stars that created them? [duplicate]

If the point in space that belongs to the collapsed star (that formed the black hole) is infinitely dense, why are black holes different sizes? Is it due to them feeding on stars and everything else ...
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Strange behaviour of black holes [duplicate]

We know black holes emit streams of radiation ,also recently discovered that they emit visible light when they eat any nearby matter . "We find that activity in the vicinity of a black hole ...
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Theoretically what happens to a black hole that evaporates?

Theoretically, does an evaporating black hole remain a black hole until it evaporates to nothing? Or does it change into something else once it evaporates to below a certain mass?
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1answer
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Why does kerr black holes have a ring shaped singularity rather than point?

I read about ring singularity on Wikipedia and didn't quite understand the flow of liquids inside a rotating body causing a ring shaped singularity with zero thickness. Moreover is it specifically ...
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Do black holes really exist?

Black holes from my knowledge are created from the collapse of a star’s own gravity crushing itself, Now my question is well two questions, is it really infinitely dense to where space-time can be ...
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Can a star eat a black hole?

I know there are stars much larger than the sun and that we've discovered "small" black holes, so, let's say that the Pistol Star, which is at least 80x the mass of the sun, and the smallest known ...
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How is the entropy of a blackhole stored at its horizon?

I read that a blackhole has an entropy that is given by the area of its event horizon (measured in Planck units). Does that mean that this information is actually physically stored there? If yes, how ...
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If a black hole has a mass of a universe what will be the volume of it?

Will it suck the entire universe in? What will the black hole look like to us, assuming we do not immediately get sucked in?
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1answer
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Could gravitational waves near merging black holes collapse to a black hole themselves?

I have understood that merging black holes emit considerable amount of their mass as gravitational waves (up to 5-10%). Based on what I have understood from gravitational waves, the closer black holes ...
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Can light be trapped in orbit?

Could rays of light be ever trapped in a constant orbit around a black hole if approached from a certain angle ? Like light hitting a glass or liquid with critical angle.
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Can we detect a black hole's radiation?

Stephen Hawking proposed that a black hole emits radiation as it evaporates. Black holes don't let any radiation escape their event horizon because even particles with the speed of light get trapped ...
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Does Hawking radiation in fact bring mass into the universe?

As I understand virtual particles pairs, e.g. electron and positron spontaneously pop into existence for tiny period of time, then they annihilate. When virtual electron and virtual positron ...
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Has a “white hole” theory been advanced to explain anomalous star formation in Sagittarius A?

In 2008, the European Southern Observatory reported, upon the end of a 16-year study described here http://www.eso.org/public/usa/news/eso0846/, that the 28 stars nearest the very large black hole in ...
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Gravastar Star With no Horizon with ultracompact and very density possible?

Is that possible with some strange Quantum Effect could give rise to a completely new kind of a star? Gravastar(Gravitational Vacuum Star) an object hypothesized in astrophysics as an alternative to ...
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Coordinates of known black holes in our Galaxy (Milky Way)

There are some articles in wikipedia with the list of known (or candidates) black holes here and list of nearest black holes. Also there is a map of Milky Way. My question is where can I get ...
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Why is frequency different for gravitational waves coming from SMBHs vs small compact binaries?

Why do gravitational waves emitted by supermassive black holes binaries have low-frequency range (~10$^{-9}$ - 10$^{-2}$ Hz) than those emitted by stellar mass compact binaries (~10$^{-4}$ - 10$^2$ ...
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How does the size of a naked black hole effect its photon sphere?

What effect does the size of a black hole have on the size or density of the photon sphere and it's proximity to the horizon? For example: A person is in space looking at 2 black holes, one of them ...
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What would a black hole merger look like?

Ship 1 is out side the black hole. Ship 2 is nearing a black hole. To ship 1 it would appear that ship 2 would be moving slower to the point it would seem like ship 2 stopped moving the closer to the ...
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Hawking Radiation [duplicate]

At the edge of black hole, matter and antimatter is created, while the matter escape, antimatter annihilate inside the black hole thus decreasing it mass. But due to immense gravitation pull, why the ...
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Measuring the size and the geometry of Universe [closed]

When we would be able to tell with surety that universe is finite or infinite? How can we exactly determine the density of the universe so, that we compare it with critical density, in order to ...
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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 ...
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minimum size for a black hole to capture a photon

If a photon is moving past a black-hole, what is the minimum size of the black-hole that will capture the photon and prevent the photon from going onto orbit around the mass? Do black-holes exist that ...
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Theoretical sudden appearance of a black hole in BBC drama show *spoiler warning*

I asked this on the ‘movies’ stackexchange site but they suggested I ask here, it’s a purely hypothetical query based on a BBC drama show called ‘Hard Sun’, feel free to kill the question if it’s ...
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Black holes and super massive black holes [duplicate]

What is the difference between a black hole and a super massive black hole?
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Is it fruitful to search for a correlation between rates of in-falling matter in black holes and the expansion rate of our universe? [duplicate]

To my understanding, white holes are hypothetical objects that are time-reversed black holes; black holes gravitationally "suck in" matter whereas white holes "spit" matter back out. As such, I think ...
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What's that ring that only now appears in black hole illustrations?

If you'll notice, space time starts to deform near the black hole, but then at considerable distance from the black hole' surface, images in the background become ultra-distorted, but then as you look ...
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If one galaxy were to collide with another, what would it look like to an immortal inhabitant of one of their planets?

I was reading this article posted on /r/space about photographing black holes, and they showed a picture of what's believed to be two black holes formed from two galaxies colliding. I didn't realize ...
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Items at the Event Horizon vs. colliding Black Holes

Items reaching a Black Hole's Event Horizon seem to be frozen in time from the point of view of an outside observer. On the other hand, Black Holes collide and merge, in finite steps, producing ...
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Can we create neutron star by pressing earth? Or other objects?

Everywhere I can hear, that if we press anything to the right size, we create black hole. Can we create neutron star by pressing, for example, our planet? And what if we press something bigger, like ...
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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. ...
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Behaviour of black holes

This question could be strictly linked to my another question related to black holes. It’s known that the horizon event is a place where dust,star components are ready to be incorporated to the ...
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Is it correct to assume that the relationship between an objects mass and size, is what decides if it’s a black hole or not?

I’m asking this question in reference to a scenario I saw posted a couple of days ago, where it’s stated that if you would shrink earth to the size of a cherry, it would become a black hole. Is it ...
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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 ...
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How can a singularity rotate?

So I've heard that all black holes that have been observed rotate to some degree. But if it has zero radius, how is it even possible for the black hole itself to be spinning? Or is it just all the ...
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The size of the radius of the event horizon of a black hole created by the merger of a black hole binary system

Let's assume that you had a black hole binary system and everything said here is possible. Their large masses would lead to a large emission of gravitational waves. The loss of orbital energy and ...
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What will the universe be like in a googolplex years time?

It will be cold and dark in 10^(10^100) years. What else can be said of the state of things in the far distant future? Will everything have fallen into supermassive black holes and then radiated ...