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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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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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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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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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 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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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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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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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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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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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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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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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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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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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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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 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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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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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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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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How can light circle a black hole one or more times and then escape again? [duplicate]

The shadow that is cast by a black hole was beautifully captured by the event horizon telescope. A concentration of light in the photon sphere around the hole (adjacent to the event horizon) ...
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How can a black hole merger create a black hole with an event horizon surface area larger than the sum of the two original areas?

Many popular and professional science sites said something about Stephen Hawking's black hole area theorem being proven observationally, finally, not just mathematically, to 95% confidence. For ...
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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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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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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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How can firewalls stay put on the event horizon?

Firewalls in black holes were introduced in relation with the information paradox. In Wikipedia we can read: A black hole firewall is a hypothetical phenomenon where an observer falling into a black ...
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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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If a black hole was headed for our solar system and would arrive within a year, would we necessarily know of it?

Basically, is our observational technology and coverage sufficient enough to pretty much always spot incoming objects like a black hole when they're a year from arriving? If so, within what time frame ...
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What if wormholes were created when a black hole and white hole collide? [closed]

Scientists have discovered black holes, white holes and wormholes but I am still unsure how they came to life. Did the black holes collide with the white hole causing a mixture of both or is there ...
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Has gain in mass from accretion onto a black hole been observed?

Have we observed a black hole directly gain mass via accretion? That is, have we observed the black hole to have mass $m_1$ at time $t_1$ and then observed its mass to be $m_2 > m_1$ at a later ...
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What is the thickness of black holes event horizon?

I would premit that I am just an enthusiast, so don't expect a good background or a deep mathematical knowledge about the topic. I just read an article about how light is reflected by a black hole (...
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How can a black hole have a charge, or be charged?

So-called 'hairless' black holes (no-hair theory, or theorem?) , which is what real black holes are, can be described by just three characteristics: Mass, spin, and charge. It is easy enough to ...
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Could we detect a globular cluster consisting entirely of black holes?

A paper recently came out in Nature simulating the evolution of the $\sim10^4M_{\odot}$ globular cluster Palomar 4 (Gieles et al. 2021, arXiv link). The authors argue that in ~1 billion years, a ...
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Would the stars look different if many primordial black holes were present?

Suppose that there are many primordial black holes. These are point masses which have a small probability to collide with stars let alone themselves. They are formed in the early universe and could ...
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Can dark matter be normal matter after all? [duplicate]

MACHO's and RAMBO's are both baryonic (and leptonic) forms of matter that can't be observed by their nature. They barely emit or reflect light. Black holes, neutron stars, or brown dwarfs (or groups ...
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If a black hole is spinning, does its singularity have a new name and what is the name? [duplicate]

Think of a spinning black hole. (Kerr black hole) Every black hole has a point of infinite density, called a singularity. When a singularity is spinning, does it have a different name? But when a ...
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Black Holes: More Than One Entry Point?

Most animations and drawings of Black Holes that I've seen usually depict some kind of funnel which is the "entrance" to the black hole; let's call this the front. Are there more than one ...
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What would I experience on a planet orbiting close to a black hole? [closed]

I can't get my head around it completely. I am standing on an Earth-sized planet circling a black hole. Let's assume the planet to be an incompressible one. It is observable that matter is sucked in ...

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