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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.

Gravitational collapse occurs at the end of a star's life, as it collapses into a white dwarf, neutron star, or (if it collapses within its Schwarzchild radius) a black hole. Gravitational collapse is also used in a theory of the universe called the Big Crunch theory, which is where scientists believe that if the universe's expansion does not exceed the space velocity, the universe will begin to shrink, ending up in either a black hole singularity, or another Big Bang (this specific ending of the theory leading to a cyclic universe).

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If dark matter only interacts with gravity, why doesn't it all clump together in a single point?

I'm a complete layperson. As I understand, dark matter theoretically only interacts with the gravitational force, and doesn't interact with the other three fundamental forces: weak nuclear force, strong nuclear force, and electromagnetism. Those are…
user151841
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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 it form galactic halos? Isn't that also an example…
Astrobuf
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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 matter into the star, but how much time will pass…
lurscher
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Why can't the degeneracy pressure self-adjust itself to resist gravitational collapse?

After a star becomes a White dwarf, it resists gravitational collapse mainly due to the electron degeneracy pressure. If the mass of the white dwarf is greater than the Chandrasekhar limit, the degeneracy pressure cannot resist the collapse any…
Soumita
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In realistic gravitational collapse, can we have an absolute horizon without a trapped surface?

In gravitational collapse, it seems that there is no close or simple logical relationship between the formation of an event horizon (absolute horizon) and formation of a trapped surface (which implies an apparent horizon). Modeling gravitational…
user4552
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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 than the Schwarzschild radius for its total…
Brian Rushton
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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 distance to the nucleus and inside the nucleus…
Deiknymi
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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?
Rene Kail
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Is it possible for a black hole to form for an observer at spatial infinity?

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 black hole. Doesn't this imply that it takes an…
DJBunk
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Can a rotating neutron star collapse to a black hole through a reduction in rotation?

It is well known that non-rotating neutron stars cannot grow without bound, since an increase in mass causes a proportional increase in density, and accretion beyond a critical limit would cause it to collapse to a black hole. However, it seems that…
Essan Verne
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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 seem to cover extensive discussion on…
L. Werneck
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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 smaller than the Jeans length, then pressure, which…
Samantha
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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 homogeneous ball of pressureless dust. My…
Jan Lynn
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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 of other "collisionless gases" such as cosmic…
PPenguin
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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 singularity inside the black hole? Can black holes…
tparker
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