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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How come the universe isn't a black hole?
This answer to a similar but imo not identical question essentially states we can be pretty sure the universe isn't a black hole, it's (for me paradoxically) too dense - more than a black hole would ...
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Since a black hole merger was detected after only 13 years of observation, can we expect frequent mergers, or was it a very improbable event?
Ligo went online in 2002, and discovered a black hole merger in 2015.
Image: space.com
Doesnt this imply that either we should expect to see another one real soon, or that we were extremely lucky to ...
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What does the "formation" of the apparent horizon of a black hole look like?
This might be a silly question, but something made me think about it recently...
Scenario 1
Let's assume, as a thought experiment, I filled a spherical volume of space with a radius slightly bigger ...
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Can the observer, who crossed the event horizon, notice the difference in metric tensor?
I get the difference between the interior of our time-like light cone(s) and the rest of spacetime that is space-like below the event horizon. Will they swap by changing space-like to time-like and ...
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If the inner horizon of a kerr black hole existed would it affect the precession of the black hole when a star orbits it?
I don't know exactly why a black hole processes but assume it has something to do with gravity from a star affecting the space outside the black hole. But would we expect the space around the inner ...
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Can black holes actually be quark stars? [closed]
Recent data and theorization suggests the possibility that stellar-mass black holes may actually be quark stars: https://ui.adsabs.harvard.edu/abs/2012mgm..conf..943H/abstract
where infalling matter ...
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"Have these giant jets spread magnetism through the cosmos [including Earth]?"
A group from Caltech led by postdoc Martijn Oei has found the largest black hole jets yet discovered. They span 23 million light-years, affecting galaxies far beyond the one they originate from.
An ...
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Would it be theoretically possible for something to orbit a black hole inside its event horizon?
I am imagining something like a small, fast-spinning, highly magnetic, neutron star.
And if it was, what would be the observable consequences, if any?
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Particle in overlapping event horizons of two black holes
Say two identical black holes approach each other so that their event horizons overlap. What happens to a particle that's perfectly in-between the two holes? It experiences the same gravitational pull ...
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What makes black hole collisions so energetic?
I recently read that GW150914, a black hole merger between black holes of 36 and 29 solar masses, converted around 3.0 solar masses into pure energy. My question is, where this this energy come from? ...
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When a mass crosses a black hole event horizon does the horizon radius get larger closer to the mass or does it increase equally everywhere?
Is the event horizon of a black hole always perfectly circular or spherical in radius or can incoming masses affect its shape?
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Why can't astronomers find evidence for small black holes?
There is no evidence for small primordial black holes that could make up dark matter.Small black holes (mass of an asteroid) at relativistic speeds passing within 6000 km of Earth could have been ...
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When a star becomes a black hole do the neutrons that are squeezed together release binding energy and if so does this energy escape from the hole?
When neutrons come together on Earth they release energy. Is this energy released from neutrons of stars as they become black holes?
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Could a black hole be shaped like a torus?
I am familiar with the Kerr metric, which states that a black hole can spin. I also know that, due to the spin, the singularity is ring shaped. I wonder, if enough spin is given to the black hole, ...
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When a black hole evaporates in its last moments, will it emit the same amount of particles and anti-particles?
Black holes are expected to evaporate due to Hawking radiation. Since Hawking temperature is inversely proportional to the mass of the black hole, as it would gradually lose mass with time they would ...
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Skewing of data regarding velocities of stars
For a school project I am currently determining the location of sagittarius A* (the supermassive black hole at the center of the milky way). I have analyzed about 1 million stars and their velocities. ...
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Black Hole Superradiance
Could someone explain what black hole superradiance is exactly and how it extracts energy and angular momentum? What is the role of the ergoregion in this process?
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In an expanding universe could black hole pairs keep orbiting each other forever?
I have always read that the accelerated expansion of the universe only affects structures that are not gravitationally bound.
However, there is a recent paper explained here which says that pairs of ...
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What is the best catalog of black hole candidates?
I posted this questions in Physics stack:
"I am searching for a catalog, list, database, etc. That should show astronomical observations of known black hole candidates. I am primarily interested ...
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Why does c show up in Schwarzschild's equation for the horizon radius?
The equation of the Schwarzschild radius is really simple, just twice the mass over $c^2$ (times a unit conversion constant that goes away in natural units).
$$ R = \frac{2GM}{c^2}$$
The question ...
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Someone explain how a naked singularity is possible
I was reading this Wikipedia article about naked singularities, however I don't really understand the how a gravitational singularity can simply exist without an event horizon. Can someone explain/...
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why would a black hole have a singularity point ? (a ring or disk seams more likely to me)
I'm not a physician nor an astronomer, I am just curious.
When I think that a star collapses, and think of large bodies that rotate.
Then it's likely that the sphere is not a perfect sphere.
Most ...
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Is the hypothetical '(Don) Page curve' of evaporating black holes equal in time, so to speak, on both sides of the curve?
I have heard that Hawking radiation is slow at first, but rapidly increases when the black hole becomes much smaller... (I forget the formula...)
Does that mean that the second half of Page's curve, ...
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What exactly is a 'gravastar'? How is it different from a 'regular' black hole?
The Wikipedia article on gravastar says that it has a 'regular' black hole metric (Schwarzschild, I presume?) on the outside, but a de Sitter metric on the inside....
What exactly does that mean?
Don'...
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Stellar Mass Black Holes and the companion star dynamics
I was studying stellar mass black holes and wondered why almost all of them had a companion star, I came through many explanations but was not satisfied, is it because its hard to detect them without ...
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Does an infalling observer ever cross the black hole event horizon in finite proper time?
I am interested in how an infalling observer perceives the plunge into a black hole.
Let me assume that actually we have three spaceships: C being at a constant distance to the event horizon, and A ...
user56648
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Evolution of black holes. Could they lose mass faster than the Hawking radiation?
As far as I understood the biggest black holes we know are at the centre of very distant quasars and they are enormous. All the big black holes are very far away. At the centre of the closer galaxies ...
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Black Hole Photon Ring
NASA recently published a video simulation of what it would look like flying into a black hole (video can be seen here ).
What confuses me is that it appears to show the photon ring around the black ...
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Does nucleosynthesis such as R Process, S Process, and P process occur in relativistic jets?
By answering a recent question about relativistic jets and their cooling I became more curious about relativistic jets. This might be a totally another sub topic on relativistic jets. But I was ...
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Why are black holes oblate spheroids?
I just heard something I have heard a million times before: "The shape of a spinning black hole is an oblate spheroid." This time, it hit me as odd that a black hole's shape changes with a ...
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Have measurements been conducted on the position of the galactic center of mass and the orbit of the presumed black hole at the center?
Related questions have been raised before
Is our central black hole actually at the CG of the galaxy?
Orbiting supermassive black hole or galactic center of mass?
, where explanations have been given ...
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Does a relativistic jet contain dust particles?
Black-holes accreting matter can emit jets of plasma that can exceed half the speed of light.
Can these jets cool off enough that dust particles condense in them? If so, could we detect flashes of ...
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A couple of questions on Hawking radiation
Black holes progressively evaporate due to the emission of Hawking radiation just outside their event horizon primarily in the form of photons. However, there is a small probability that they emit ...
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Moon mass object hitting Earth vs Moon mass blackhole hitting Earth damage comparison
Doesn't a blackhole do less damage if it goes fast enough to be able to escape fast enought but a moon-mass object if going faster does more damage? Is this true or would a black hole do more damage?
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How ultra massive black holes would " disrupt the accretion discs that feed them" beyond some upper limit to their masses?
According to this,
How big could a black hole get
recent studies suggest that UMBHs cannot physically grow much beyond
this (10 billion solar masses) anyway, since they would then begin to
disrupt ...
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Black hole explosion due to rotation [duplicate]
I am not an expert, I was just thinking about this scenario:
A black hole that, for some reason, will start spinning faster and faster. Is it theoretically possible that the rotation becomes so fast ...
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Is there evidence against a Universe Black Hole?
As far as I know, the critical density of our observable universe coincides with the density of a huge black hole of the same radius. It could be a BH expanding at the speed of light and growing in ...
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What are the most up to date, accepted, evolution stages of big stars that end in compact objects or a planetary nebula?
There are numerous charts and diagrams showing the stages of stellar evolution, as:
or
among many more (you can find several after googling a little), for example.
When I studied my B.Sc. on Physics,...
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What would happen if a low-mass primordial black hole was captured by a brown dwarf or planet mass object?
Prompted by a recent PBS SpaceTime video
The video in question discusses what would happen if a low-mass (asteroid-mass) primordial black hole were captured in the core of a Sun-like star (a so-called ...
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What would happen if a small black hole fell into a star?
Let's say you created a cannon that can shoot small black holes and you shoot it at some star.
Would the star just turn into a black hole silently? Or rather first destabilize and produce a last ...
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Could an hypothetical hidden black hole companion to the sun be revealed by proper motion data?
If the Sun were in a binary star system with a black hole companion, the Sun would be orbiting the black hole, and this should be reflected in a change in the observed proper motion of nearby stars.
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Why do we not call black holes black stars or dark stars?
I've never understood why the term black holes are widely used to describe what is actually a black star or dark star. I mean why name something just because of its extreme space curvature effects? In ...
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How can Kerr black holes have a 'speed limit' to how fast they can spin?
Obviously, the speed of light is a presumed limit, at least for 'physical' objects moving 'within' ('through'?) spacetime, but...
In recent news some scientists believe they have figured out the ...
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Can black holes even exist [if mass cannot be retained near the collapse threshold]?
A black hole happens because enough material mass exists in an area to create a gravitational field strong enough that nothing escapes (including light). This gravity also exceeds the strength of ...
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Amount of black holes over time
Hello the number of black holes is much bigger than the number of black holes in the past right?Let $b$ be the number of black holes in the universe.Obviously $\frac{db}{dt}>0$ but what about $\...
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JWST Early Black Holes: Gas Collapsed To Metallic Hydrogen Core?
I was reading an article about early black holes found by JWST at Redshift 9. And saw that there was wonder at how large amounts of gas could collapse into a black hole as a theory.
So my question is ...
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Are gravitational waves emitted equally in all directions?
I have a question regarding gravitational waves that I can't figure out. Hope some wise minds here can help a simple amateur without technical or scientific education.
Two black holes rotating around ...
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Black hole collision
In a situation where 2 black holes are close to colliding, but do not collide, can one black hole free/steal matter from the other in passing if the event horizons brush?
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From an outsider's perspective, how can a black hole grow if nothing ever crosses the event horizon?
Due to time dilation, an outside observer never sees a falling object actually cross the event horizon. I'm not referring to the optical illusion of red-shifted light making objects appear to fade ...
user52416
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Possibility for black holes having negative energy
new to the community here. The question I have is whether black holes can possibly contain negative energy of any sort?
It’s not a carefully thought-out question as space is not my bailiwick.
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