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Questions tagged [gravitational-collapse]

Use for questions related to the creation/possibility of black holes in a certain situation, singularities, the contraction of an astronomical object due to its own gravity, and the re-collapse of our universe. Do not use for questions relating to normal gravitational attraction.

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1answer
77 views

Would a “naked singularity” and a spinning black hole behave the same?

So I've been doing a lot of research on spinning black holes and fumbled upon the concept of a "naked singularity" where a gravitational singularity exists without an event horizon. Ignoring the ...
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0answers
13 views

Comoving system of expanding or collapsing dust-like particles

I have a question on comoving and synchronized reference systems. I read the corresponding section (97) on Landau/Lifshitz's second book field theory on it. In particular it is said that space ...
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2answers
58 views

Dark Matter Stars Triggering Nebula Collapse

I'm interested in theories of dark matter where dark matter is an equivalent copy (or copies) of ordinary matter. Each equivalent sector is hidden from the others would see the others as 'dark' and ...
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0answers
23 views

Is there a de Sitter or FRW collapse solution for black holes, similar to the Oppenheimer-Snyder-collapse?

I know the Oppenheimer-Snyder-solution and the formation of the black hole event horizon during the collapse. Is there a similar solution for a dynamical collapse, embedded in asymptotic de Sitter ...
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2answers
87 views

Is there an equation for the amount of energy from a collapsing star BEFORE it creates a black hole?

(I could be phrasing my question incorrectly, so bear with me as I try to explain it.) Recently I've been very interested in the geometry and physics of black holes, so I started messing around with ...
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592 views

Gravitational waves and chirp waveform

When two neutron stars collide emitting gravitational waves, what exactly does the chirp waveform represent and how is it used to infer the distance to the source?
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2answers
53 views

Calculation of Gravitational Collapse time

The answers to Gravitational collapse and free fall time (spherical, pressure-free) describe the calculation of collapse time for a gas. For the case of neutral hydrogen gas with number density $10^4$/...
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1answer
58 views

Naive question about Gravitational collapse

Suppose that you have a probe orbting a $10M_{\odot}$ star in the final moments before gravitational collapse. In a time $t$ the collapse event occurs. So do you really would see all the matter "...
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1answer
46 views

Do cosmic voids have to exist to prevent gravitational collapse of the Universe?

Since a black hole radius is 2 times the mass, it seems like any infinite distribution of matter has to have voids of increasing size as the scale changes in order for the whole Universe not to ...
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1answer
54 views

Do binary black holes mergers emit light?

I am not referring to Hawking radiation and although I see there should be no way the collision can produce electromagnetic wave after all, a black hole is simply a region of space right?
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1answer
60 views

Would a neutron star-like celestial body made of bosons collapse because of missing Pauli repulsion?

Imagine the neutron star-like celestial body would be built up of bosons (assume that neutrons would be bosons). In that case there would be no Pauli repulsion (the exchange force of the exchange ...
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1answer
70 views

When a star undergo collapse in a binary system what effect it has on its companion star? [closed]

when a star in its lifetime fuses up all its hydrogen and then collapse under gravitational force, till the temperature inside become high enough to restart the fusion of helium and radiation pressure ...
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3answers
263 views

How does gravity cause nuclear fusion in stars?

I am a bit confused regarding the nuclear fusion that occurs during star formation. For example, suppose there is a huge hydrogen cloud. It gets more mass and therefore pulls in more and more hydrogen,...
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1answer
395 views

Oppenheimer-Snyder Collapse

I have read the Oppenheimer-Snyder collapse is significant in the sense that it was the first work which treated the problem of black hole formation under gravitational collapse. The model assumes a ...
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1answer
85 views

Are the actual singularities with geodesic incompleteness the same as curvature singularities?

Types of singularities include curvature singularities and conical singularities. So, for a curvature singularity(black hole) with geodesic incompleteness, is it the same as a physical singularity? If ...
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1answer
31 views

What's Gravitational Potential Energy of a Balanced Mass on a single Point?

Anyone know how to calculate the gravitational potential energy of a balanced Mass such as an upside down 2d triangle balanced on a single point. Is there any way to calculate the gravitational ...
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1answer
150 views

Are physicists still ignorant of the existence of real singularities?

(1) Is the gravitational singularity (or space-time singularity) the same as the black hole singularity? (2) The wikipedia page says Physicists are undecided whether the prediction of ...
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2answers
140 views

Gravity/Energy relationship

I understand that gravity is not energy, but is force, but my question revolves around if the presence of gravity in the universe results in a continuous amount of energy, from gravity-induced ...
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1answer
201 views

Free fall time of collapsing non-rotating star in GR according to a distant observer

Suppose a star with a spherically symmetric mass distribution, mass $2\cdot M_{sun}$ and initial radius $R$, undergoes a gravitational collapse after all gas pressure has vanished. The final radius ...
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1answer
58 views

Formation of Black holes from smaller bodies

Black holes are formed when the supermassive stars collapse under their own gravitational force. But why they should be supermassive. The gravitational force is also present in smaller bodies like ...
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2answers
850 views

Questions about the Jeans length

I have a couple of questions about the Jeans length. Suppose the universe has a homogeneous energy density, except there's a spherical region that is overdense. I understand that if the region is ...
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5answers
107 views

How does gravity acts on the electrons to collapse a neutrons star or white dwarfs against the degeneracy pressure?

if electrons is considered as quantum particle in case neutron star (alluding to quantum statistics) how does gravity makes the star collapse? considering the fact that electrons are quantum particles ...
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1answer
269 views

Is it possible for a black hole to form for an observer at spatial infinity? [duplicate]

To my knowledge if you calculate the coordinate time (time experienced by an observer at spatial infinity) it takes an infinite amount of time for an object to fall past the horizon of a Schwarzschild ...
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1answer
85 views

How does a distant observer see matters that “form” an initial black hole?

I did see Can black holes form in a finite amount of time? but it does not seem to discuss how a distant observer would see evolution of collapsing matters that form a black hole. Does it view these ...
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1answer
143 views

Numerical relativity resources - Adaptive Mesh Refinement

I have, in the past few months, been studying numerical relativity, specifically the problem of spherical collapse of a scalar field as studied by Choptuik. I have also taken a look at some books that ...
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1answer
143 views

How do I calculate the actual gravitational potential energy between two objects $m_1$ $m_2$ that are at zero distance?

How do I calculate the gravitational potential energy between two objects that are separated by near to infinite distance? I would like to know if the two objects are kept at near infinite distance, ...
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0answers
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Elementary flatness - Gravitational collapse of a massless scalar field

Choptuik pioneered numerical studies of the gravitational collapse of massless scalar fields in spherically symmetric, asymptotically flat spacetime. In his papers (e.g. https://arxiv.org/pdf/gr-qc/...
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1answer
352 views

Gravitational collapse of dark matter [duplicate]

The gravitational lensing evidence suggests the existence of massive and relatively dense regions of dark matter. However, if dark matter interacts only gravitationally, what would stop it from ...
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0answers
140 views

In what sense is ''Oppenheimer-Snyder collapse a time reversed closed FRW model"?

In what sense is ''Oppenheimer-Snyder collapse a time reversed closed FRW model" ? That is, "Are closed FRW metric (k=1) and the geometry inside the collapsing homogeneous matter same?" If yes, how? ...
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2answers
100 views

Need proper interpretation of imploding/exploding self-gravitating sphere

While searching for some nice and simple problems in Newton's theory of gravity, I've made this trivial calculation for which a proper physical interpretation is lacking. Some pieces are missing and ...
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1answer
81 views

What are the conditions for non-spherically symmetric gravitational fields in GR?

This may seem like a silly question. However, what are the conditions for a matter source to produce a non-spherically symmetric gravitational field? More specifically, can a spherical source ...
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4answers
3k views

Throwing a micro black hole into the sun: does it collapse into a black hole or does it result in a supernova?

What do we know about accretion rates of micro black holes? Suppose a relative small black hole (mass about $10^9$ kilograms) would be thrown into the sun. Eventually this black hole will swallow all ...
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1answer
120 views

Do galaxies have a halo of neutrinos and cosmic microwave background?

If virial arguments as in "How can dark matter collapse without collisions or radiation?" allow concluding that dark matter could collapse to galactic halos purely gravitationally, then is this true ...
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4answers
3k views

What happens during gravitational collapse to cause the formation of a star?

I know that stars are formed from dense regions in large gas clouds. I know that when gravity causes the mass of the clump to get so big that its internal pressure can't sustain it, it collapses and ...
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0answers
209 views

What does black hole formation and evaporation actually look like as viewed from far away?

Many people on Physics SE (myself included) have been confused about what black hole formation and evaporation look like when viewed from far away. For example: Does any particle ever reach any ...
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1answer
86 views

Photon gas into a Black hole

Can a photon gas have so much energy that it collapse into a black hole just like a regular star?
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0answers
146 views

What is more dense, Neutron Star material, or Black Hole material? [duplicate]

What is the most Dense material in the Universe? Is it Neutron Star Material? I would think that the Singularity in a Black Hole would be the densest material, or the material that exists moments ...
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1answer
282 views

Gravitational collapse (conservation of energy)

During gravitational collapse, gravitational potential energy of the gas is converted to its internal kinetic energy so the internal energy of the clous of gas is said to be increased But isn't ...
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1answer
75 views

Can a theoretical object exist as such that its mass overcomes gravitational collapse

A daydream the other day led me to the question if "a universe filled with water (or any other substance for that matter), instead of being mostly void" could exist within the rules of our current one....
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1answer
132 views

Negative mass thin shell collapse

Suppose we have a collapsing light-like (ingoing) shell with negative mass and decreasing further. The shell is radiating and so the exterior region is that of the outgoing Vaidya solution. $$ds^2 = -...
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1answer
35 views

Will a collapsing black hole be ensured to be in eternal equilibrium at some point?

I'm just even if at all hobbyist in this matter. I learned that stars will collapse at some point and go supernova or turn into black holes if not able to keep equilibrium. But what happens in the ...
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0answers
71 views

Would a grid of $10^{57}$ hydrogen atoms collapse?

Assume we have a gridded cube of $10^{57}$ hydrogen atoms, with all atoms 1mm apart from other atoms. This 'cube cloud' is in an area of space that would otherwise be at zero g, were it not for the ...
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1answer
308 views

What does singularity mean in the context of black holes? [duplicate]

Non-rotating big stars can be subject to a gravitational collapse increasing their density. When the density is so high that the mass volume shrinks below the event horizon, a black hole is formed. ...
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2answers
1k views

What is the main thermal energy source for a protostar, the contraction or the deuterium burning energy?

According to the virial theorem, when a protostar contracts, half of the gravitational potential energy is radiated and half is kept as kinetic energy of the falling material which in turn heats the ...
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1answer
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How can dark matter collapse without collisions or radiation?

I understand that dark matter does not collapse into dense objects like stars apparently because it is non-interacting or radiating and thus cannot lose energy as it collapses. However why then does ...
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0answers
193 views

Situation after Saini & Stojkovic's paper on unitarity in gravitational collapse and non-formation of black holes?

In their paper, Anshul Saini and Dejan Stojkovic [1] claimed that by calculations it is possible to demonstrate that in a gravitational collapse of a disk, an event horizon is never made for a far ...
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1answer
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What happens to atoms inside a black hole?

Black holes have very high gravitational force that tends to crush everything. So as we know atoms in a molecule have inter-atomic spacing between them and further electrons also revolve at a certain ...
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2answers
121 views

Direct rocky planet formation without protostellar disk?

Inspired by this question, which sort of asked what I'm asking, but emphasized a different point (and the answers accordingly addressed that). Can a rocky planet form directly from the collapse of ...
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1answer
491 views

Gravitational collapse of a photon cloud

The Schwarzschild solution shows that a spherically symmetric, static fluid will undergo gravitational collapse if too much mass-energy is concentrated together (i.e. if the fluid's radius is less ...
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1answer
275 views

Electron degeneracy pressure

Why is it that in stars undergoing gravitational collapse electron degeneracy kicks in? Why couldn't the electrons form energy bands like in semiconductors?