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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Have any HCSSs (supermassive black holes with a tight bunch of gravitationally bound stars) ever been detected?

This article from sciencealert states: Astronomers think these two galactic cores could merge into one larger black hole, sending huge gravitational waves rippling out across spacetime. But if there'...
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How, precisely, do radio astronomers detect (and record) the phases of waves for interferometry?

Interferometry is always in the news, and at radio frequencies it has been for a long time... The popular press always talks about directly 'interfering' two waves as they come in, but can they tell ...
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Can we compress any object to create black Holes?

In general, when a star runs out of nuclear fuel, gravity gets the upper hand and the material in the core is compressed even further and creates black holes. I am clear till here. Now the question ...
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How did the Universe climb out of its own Big Bang black hole?

The Big Bang started as a singularity. That means small. All the matter in the universe was in a volume smaller than its own Schwarzchild radius. The universe was inside a black hole. At present, the ...
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The question regarding ZTF20acigmel space event detection

I have a question re аrXiv preprint article: https://arxiv.org/pdf/2110.05490.pdf It describes the detection of a space event, dubbed ZTF20acigmel, which was a massive explosion in a galaxy located ...
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Is there a comprehensive catalog of all known black holes? [duplicate]

Is there a comprehensive catalog of all known black holes? If "yes" - does it include the method of the black hole discovery and it's location in the Universe? Are black holes, detected only ...
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Is there an official list of objects in the sky?

I would like to know how many known quasars there are in the Universe as well as x-ray binary black holes (not Neutron stars) but I don't seem to be able to. I also want to know how many black holes ...
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Does general relativity imply that singularities cannot exist?

General relativity states that all matter in the universe is moving forward through spacetime at the speed of light. Objects that are stationary in space travel at c along the time axis, and objects ...
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Has the Advection-Dominated Accretion Flows (ADAF) model been used to describe accretion flow around a rotating black hole?

I am studying Advection-Dominated Accretion Flows (ADAF) from the review paper Advection-Dominated Accretion around Black Holes. In section 2.1 of the paper, the authors provide the basic equations of ...
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What if hypothetically Ton 618 could have been a star

Assuming Ton 618, the largest ultra massive black hole wasn’t the result of feasting on near by matter but was hypothetically once a single star body. How large in terms of size would TON 618 have ...
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What will happen if a black hole appears near our solar system?

We know that a black hole possesses immense power and can destroy anything coming in front of its path. If such a black hole appears near our solar system, are we going to survive? Is there any way ...
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What does 's' or 'ds' or $ds^2$ mean in the Schwarzschild equation(s)? [closed]

And: These are from Wikipedia on Schwarzschild metric, Derivation of the Schwarzschild metric and the last is from Science Direct, Schwarzschild metric.
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Does the Canis Major Dwarf Galaxy have a black hole at its centre?

I am just wondering: is there a potential galactic centre out there that's very close to us? I know that CMDG is irregular, but can it still contain a black hole at the centre?
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Super conductivity of black holes

As we all know that we cannot see black holes due to its strong gravitational force. But I think gravity is not the cause for invisibility of black holes. The temperature of a black hole is 1.4×10^-...
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How does Hawking Radiation work exactly?

I know that a particle and anti particle, virtual particles, spawn at the edge of an event horizon, and one particle falls into the black hole, and the other goes out, but how does the other know how ...
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How come a "failed supernova" is, well, "failed"?

I heard about this a while ago but recently came back to it: https://en.wikipedia.org/wiki/Failed_supernova which suggests that basically what this is is something where a star is so big and heavy ...
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M87 Black hole. Why can we see the blackness?

So, as the title states, why are we able to actually see the 'blackness' of the black hole? I get that what we are actually seeing is the event horizon, or accretion disk. But should this not extend ...
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Does the density of a black hole decrease after releasing a large amount of Hawking radiation?

Is is true that the smaller a 'regular', stellar-mass black hole is, the denser it is inside of its event horizon? After all, if you look up (or calculate) the Schwarzschild radii of the Sun and the ...
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How well conserved is etendue in extreme gravitational lensing scenarios?

This excellent answer to Could dark matter exist in the Universe in the form of sufficiently dense objects? includes the following image and description: Light from the background galaxy circles a ...
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Most time dilation possible outside of the event horizon?

What is the most time dilation possible outside of the event horizon of a black hole with the reference to us? I know that time dilation is stronger if you are near an extreme amout of mass. It is ...
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Is gravity affected by time dilation? [closed]

I just thought about what time realy is but I can't put my head around this so I was thinking that if time dilation happens at the edge of a black hole that just everything gets slower. But does ...
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What methodology should be used to choose the correct model for origin of QPOs in X-ray astronomy?

In X-ray astronomy, quasi periodic oscillations (QPOs) are routinely shown by black hole and neutron star X-ray binary systems in their X-ray flux. Despite being strong and easily measurable signals, ...
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How can a black hole stop light from being emitted when all observers see light traveling at the same speed? [duplicate]

Quite literally every science show talks about black holes with a similar phrase: so dense that nothing, not even light, can escape. Let's say I am in space a safe distance from an object. I drop an ...
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Could a black hole's accretion disk be bright through natural means?

This question is based on this description of the Cormoran Supermassive Black Hole in the Orion Arm's website: Surrounding this event horizon is an (apparently artificial) accretion disk about 4AU in ...
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In what year (2014?) the gravitational wave triggered by this merger was possibly generated?

Re: "A transient radio source consistent with a merger-triggered core collapse supernova" https://www.science.org/doi/10.1126/science.abg6037 Actually the described merger consisted of two ...
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What observation methods could confirm hypothesis that primordial black holes formed from Fermi balls are the source of dark matter in the Universe?

https://arxiv.org/abs/2106.00111 What astrophysical observation methods could be used to confirm the above hypothesis that primordial black holes formed from Fermi balls are the source of the dark ...
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What is the maximum possible peak power during a black hole merger?

The peak power output of the GW150914 black hole merger was 3.6e49 Watts. These black holes were around 30 solar masses each and about 3 solar masses were converted to gravitational waves during the ...
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Is the event horizon the defining characteristic of a black hole?

I was wondering about the characteristics of a black hole, and I know they have mass, spin, and an insanely strong gravitational force. But, as far as I know, basically all black holes possess the ...
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Does the combination of concepts of "cosmic sensorship" and "Gregory-Laflamme instability" correlate with the "string theory"?

Does the combination of concepts of "cosmic sensorship" and "Gregory-Laflamme instability" correlate with the "string theory" since it appears that both require ...
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Is a black hole's gravity strongest at its event horizon or at least near it?

I know black holes are extraordinarily powerful when it comes to the gravitational pull. But I wanted to get something clarified - is the gravity stronger at the event horizon (like, on the very edge ...
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What effect does time dilation have on bodies orbiting close to Black Holes?

As far as my (somewhat basic) knowledge of astrophysics goes in general the closer to a star your orbit gets smaller (because you travel less distance) and faster (because you're deeper in the gravity ...
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Are there automatic methods to locate (stellar and supermassive) black holes?

Black holes have been discovered using several techniques, as outlined by How are black holes found?. What I was wondering is: are there automatic methods for locating them (e.g., artificial ...
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Why is the statement "black holes make up 1% of the mass of the Milky Way Galaxy" unknown?

a) We cannot detect all black holes and therefore don't know the percentage of the galaxy's mass they make up. b) We do not know the mass of the Milky Way's central black hole. c) According to our ...
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What happens inside a massive collapsing shell?

I have already asked this on the physics site. I am not sure where it fits better. Consider a massive spherical shell collapsing under its own gravity. Say the mass is that of one galaxy. The ...
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Astronomic objects (and their distribution functions) appearing in an old computer game?

Many decades ago, when I learned coding, I was also reading a (red) book on the programming the 8080 processor which was full of code listings and their description. I was in particular fascinated by ...
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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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Could we see small objects like animals on an exoplanet using Solar Gravitational Lensing (SGL) if we could use any star or a black hole for lensing?

Theoretically, if a telescope is positioned in a focal point of a supermassive black hole or a star much more massive than the Sun, would there be a limit to how far away an observable planet can be ...
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If Newton said a sphere acts as if its entire mass is at its center,why are there no black holes between any two ordinary stars of 4 Solar Masses?

A paper('A QuasiHeuristic View On The Occurrence Of Singularity Forms of Ordinary Matter') discussed at a recent colloqium at our institution postulated,since 4 Solar masses is what is needed for ...
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Would an object falling into a black hole ever collide with the surface of the black hole? [duplicate]

If an elephant jumped into a black hole would it ever splatter on the surface of the black hole? Or would it continue to fall indefinitely? I think the elephant would continue to fall away from ...
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What actually is the mass? [closed]

Since high school, I've been told that the definition of mass is "quantity of matter" (which is absolutely wrong, I guess). If mass is actually a quantity of matter and it is a measure of ...
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What is a typical "pulse rate" for a black hole "heartbeat"? Is the process better understood than it was in 2011?

The 2011 NASA Goddard video NASA | RXTE Detects 'Heartbeat' Of Smallest Black Hole Candidate mentions a heartbeat and includes a graphic of pulses from GRS 1915+105. A screenshot is shown below. No ...
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What is a wormhole?

I have learned that there are white holes and black holes in the universe, but I am confused as to what a wormhole is. Is it a tunnel that connects black and white holes?
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What is the concept of wormholes? [duplicate]

My main queries for now I guess: What is the theory behind wormholes? What is the possibility and likeliness of their existence based on scientific analysis, not conspiracy theories? What is the ...
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Why do some call the no-hair conjecture the no-hair theorem?

This excellent answer to Why would a black hole's magnetic hair being short-lived not violate the no-hair conjecture, but long-lived hair would? How long is “long-lived”? has got me thinking because ...
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Could observation of GL or other image phenomena from system of 2 merging massive dense objects and of GW caused by their merge be connected?

What is the probability to observe gravitational lensing (or any other image related phenomena) from the pair of black holes (or pair of neutron stars or black hole - neutron star) which are about to ...
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Why would a black hole's magnetic hair being short-lived not violate the no-hair conjecture, but long-lived hair would? How long is "long-lived"?

Phys.org's Magnetic 'balding' of black holes saves general relativity prediction says: There is a potentially hairy threat to the conjecture, though. Black holes can be born with a strong magnetic ...
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Cryogenic black holes

In a hypothetical case take a hydrogen gas. If we start cooling it down to the point where its core temperature is 0 K, does the electrons become still and fall into the nucleus due to the fact ...
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Are there black holes and neutron stars in satellite dwarf galaxies orbiting around Milky Way?

It is thought that the number of satellite dwarf galaxies orbiting around Milky Way is counted in hundreds. Are there black holes and neutron stars in satellite dwarf galaxies orbiting around Milky ...
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Is there a minimum distance between two black holes in a binary system beneath which it can't be observed as a binary?

Suppose two black holes are observable by means of their lensing effect. If these holes are orbiting around each other, then is there a minimum distance from each other to be still observable as ...
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Can single black holes be observed by its lensing effect?

A comment on a question I asked left me confused. I asked about the possibility of observing a binary black hole by examining the lensing the binary produces. A binary has a different lensing effect ...

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