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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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Could an object, assuming possible, escape black hole by travelling above constant speed?

I am always hearing that after travelling inside a given BH's event horizon, the escape velocity is greater than c, which makes it impossible to escape. Suppose an ship is inside a BH. Assume it is ...
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Can gravitational waves pass through a black hole?

As the title says, what happens when a gravitational wave approaches a black hole? I would presume that something interesting happens because of the way spacetime works near black holes but I have no ...
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What happens if I were to add angular momentum to a maximally spinning black hole? [duplicate]

I am aware that a "naked singularity" is not possible. However, what would happen if I added angular momentum to a black hole near the maximal angular momentum limit? Does it asymptote?
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Black hole density

How does more compression relate to a stronger gravitational pull. Like, when we say that a black hole is a tiny space that has 20-30 suns compressed in it, how does this increase its density and ...
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How does the black hole at the center of M87 look like in the visible spectrum?

I learned here that the picture of the black hole we saw all over the news was a false color image, based on the radio spectrum emissions. How would the black hole at the center of M87 look like when ...
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Where is the intervening light in the M87 black hole?

The M87 black hole is at the centre, more or less, of an elliptical galaxy of 1 trillion or more stars. So certainly there are stars and other light emitting objects (emission nebula e.g.) in the ...
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Why does the Event Horizon Telescope (EHT) not include telescopes from Africa, Asia or Australia?

The Event Horizon Telescope seems to include these radio telescopes currently: Image by European Southern Observatory (ESO)/O. Furtak; CC-BY 4.0-licensed, see the source on Wikipedia Commons and the ...
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If a black hole does not emit light, how can one take a picture of the black hole itself?

There's some discussion that the image composed by the Event Horizons Telescope is really just an accretion disk. To "take an image" of something, you need the light reflecting off of the surface of ...
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Do the “schwarzschild metric” or the “isotropic metric” fit the Event Horizon telescope data on Messier 87 better?

The "Schwarzschild solution" in "Schwarzschild metric" looks like: $$\text -c^2d\tau^2=-\left(1-\frac{2GM}{rc^2}\right)c^2dt^2+\left(1-\frac{2GM}{rc^2}\right)^{-1}dr^2+r^2(d\theta^2+\sin^2\theta\,d\...
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What is the actual visual characteristics of a black hole?

Is there a safe distance in which a black hole can be observed with the human eye? What is a safe distance? I have seen many computer simulated and artist renditions, and I am not sure if they ...
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Where is the matter that has fallen inside a black hole?

Matter once it crosses the horizon of events is definitely forced to enter the black hole without the possibility of escaping from the intense gravitational field, so much so that even light can not ...
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What does it mean when we say that information is potentially recoverable from a black hole

My understanding is that if the surface of a black hole is holographic, then information is potentially emitted from a black hole, say due to Hawking radiation or some other means. What can say ...
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Why is the ring of light around the M87 black hole bigger than the photon sphere?

Today we know that a black hole represents a region of space where the gravitational forces are very intense, this consequence of a concentration of matter in a very small region of space. On April 10 ...
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Why isn't the relativistic jet visible in the image of the M87 black hole?

I'm referring to the infamous relativistic jet, which consists of matter being accelerated to near the speed of light, originating at the poles of the black hole: But in the image of the black hole ...
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Why not capture also Milky Way's black hole image? [duplicate]

The world has now seen the black hole "close-up" of M87. Besides the recognition to how awesome science has become in the 21st century, I have the following question. Didn't they work also to ...
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Why the chosen orientation for the M87 black hole image?

By now we are all familiar with the official image of the black hole in M87: Now, in the universe, as far as I know, there is no up and down, nor left and right. All is relative. Hence my question: ...
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M87. What was the black hole before?

10 seconds before the M87 black hole was a black hole, what was it? A star 10 times the size of our solar system?
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What resolution would earth-moon telescope achieve?

Event horizon achieved earth-size telescope by using seperate telescopes around the world to interpolate an image of a black hole at resolution of 60 arcmicroseconds. What resolution could we get if ...
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What is the light source in the black hole images?

What is the light source in the black hole images? I've searched the site before asking, as well as tried to google it. But perhaps the answer is buried due to the recent news. My understanding, is ...
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Why isn't the black hole white?

I recently saw the first image of a black hole. As I understood, it is covered with bright, hot matter. In this case, how can we see the black disk (event horizon), instead of a bright disk due to the ...
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Why don't we see the gas behind the black hole?

In computer simulations of what a black hole might look like and many artist renderings of black holes, they all seem to show the brightly glowing gas BEHIND the black hole due to gravitational ...
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What description of the image can we expect from the image of first black hole? [closed]

The EHT has published the first image of a black hole. I was wondering what could be the size of the original image of the first black hole and the format of the image captured?
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Event Horizon Telescope Data Cleanup

I was wondering how the researchers were able to minimize or neutralize confirmation bias regarding the data collected? As I understand it, the algorithm pruned much of the data, which would make ...
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Does the “photo of a black hole” taken by EHT actually depict a visible light-based scenario?

I'm still at my bachelor of electronic and communications engineering, so I'm not an expert of radiotelescopes; however, I surely know that, typically, radio communications are characterized by a RX ...
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If blackholes are spherical, what is the prespective of the blackhole image?

If black holes are spherical, so shouldn't it be absorbing light from all the directions? How would one explain the light ring. which seems more like a 2D ring than a sphere?
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What part of the EM spectrum was used in the black hole image?

The EHT has published the first image of a black hole. It is the event horizon of the singularity in M87 against its accretion disk. I've been through the reports in the popular press but none ...
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Do the actual false colours in the M87 black hole picture convey information?

As for the title. The picture could have been plotted in grey scale, B&W, whatever couple of colours, or perhaps using a window of wavelength in order to show shift of the Doppler/relativistic ...
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Is this the best non-radio image of whatever's at the center of M87? How was it taken?

The BBC News article First ever black hole image released shows the instantly-iconic radio image of the (almost certainly) supermassive black hole at the center of the M87 galaxy, just released by the ...
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Why are there uneven bright areas in this photo of black hole?

In the recently released photo of a black hole shown above, which was created by using data from EHT, why is the lower region brighter than the one above? Is it because of the rotation of the ...
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What is the smallest diameter black hole that can be formed naturally?

I was watching the video I Put a 1mm Size Black Hole Next to Earth and This Happened - Universe Sandbox 2 discussing what would happen if a 1 millimeter black hole is orbiting the earth, and I began ...
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Why not take a picture of a closer black hole?

There are closer galaxies than Messier 87 for sure, even ours! It sparked my curiosity that they went with one 53 million light years away. Is there a reason for this?
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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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Is there any difference between M87's image and predictions?

Today, the EHT released (somewhat blurry as compared to simulations)images of M87 blackhole. Did the image contain anything which might lead to a correction to General Relativity or were all the ...
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Why didn't the Event Horizon Telescope team mention Sagittarius A*?

At the press conference this morning, the Event Horizon Telescope team didn't say much about Sagittarius A*, which was the target many of us have been waiting for. Is there any explanation anywhere ...
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Why did the Event Horizon Telescope take so long to take a photo of a black hole?

The Event Horizon Telescope is in the news now because they are about to release the first ever picture of a black hole. They have been working on this since 2006. Why did it take 13 years to produce ...
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Discontinuity in space-time

What I understood about it till now is that space-time fabric is kind of broken there. Please tell me whether I am correct. If it's true then does it mean that perception of time will stop there? I ...
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Are gravitational waves part of dark energy?

Do the current models of the universe consider the energy release of gravitational waves? E.g. iirc, the last black hole merger detected had a gravitational wave energy equal to ~3 solar masses (hope ...
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Why does gravity make time go slower and warp light?

I know that objects with lots of gravity are capable of warping light or slowing time (an example being a black hole). I also know this is because of the theory of relativity, but I need someone to ...
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Mini disk of a blackhole meaning

What is meant by the "mini disk" of a blackhole? Is it the same as accretion disk? If not, whats the difference? Eg: In the abstract of this paper https://arxiv.org/abs/1806.05697 it is mentioned "...
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Does matter accelerate to the speed of light as it approaches the singularity?

$$v_\mathrm e=\sqrt{\frac{2GM}r}$$ If we understand the escape velocity to be the speed needed to escape from the 'surface' of a gravitational object described by the above equation. It is equally ...
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Mass of a potential black hole in a binary system

So I've been given the velocity curve, parallax and apparent magnitude of a star in a binary system with what is potentially a black hole. I've calculated from the apparent magnitude and parallax that ...
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Is a black hole a three-dimensional or four-dimensional object? [closed]

Is a black hole a three dimensional or four-dimensional hole?
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Why does the author believe that the central mass that gas cloud HCN-0.009-0.044 orbits is smaller than our solar system?

Phys.org's Hiding black hole found says: A research team led by Shunya Takekawa at the National Astronomical Observatory of Japan noticed HCN-0.009-0.044, a gas cloud moving strangely near the ...
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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 did the authors determine both the spatial size of gas cloud HCN-0.009-0.044 and its central mass at the same time?

Phys.org's Hiding black hole found says: A research team led by Shunya Takekawa at the National Astronomical Observatory of Japan noticed HCN-0.009-0.044, a gas cloud moving strangely near the ...
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Singularities/ringularities and their properties

A black hole contains a singularity at its center. It is a zero-dimensional point, and it's where all its mass is located. So, my first question is: If a singularity contains all a black hole's mass,...
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Smallest mass of star to be a black hole? [duplicate]

It seems to me that I forgot the smallest mass of a star and its angular momentum in order to form a black hole. So I know that electron degeneracy pressure is overcome if the core is 1.4 solar ...
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Can Earth be ejected out of the solar system this way?

I found this image of what maybe a model of our solar system. Without a credible source I'm not sure I am looking at a star or black hole that comes close to our solar system and how it could throw ...
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Possible to use tachyons to explore black hole?

I read on a Wikipedia article lately that tachyons are theoretical particles which always travel at or above the speed of light. That means that when one passes us, we see two images, a blue shifted ...
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What happens if a black hole is produced inside another black hole?

Similar question here. The question I linked got me thinking. It is known that a black hole doesn't let anything escape its event horizon, not even light. Thus, naturally, anything that passes the ...