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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If a photon were 1 Planck length away from the event horizon of a blackhole, would it be able to escape the blackhole's gravitational pull?

I understand that one could theoretically replace the sun with a blackhole without affecting the orbits of the planets. This leads me to believe that a blackhole isn't a "cosmic vacuum cleaner" so ...
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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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Mass of Photon and Black holes [duplicate]

The gravity caused by a black hole is said to be so strong such that even light(photons) can not escape from it. since gravity exist only in between objects with mass, How does a black hole attract a ...
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Could an object, assuming possible, escape black hole by travelling above constant speed? [closed]

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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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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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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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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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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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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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 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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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What defines the plane of an accretion disk around a black hole?

The question Do we know at which angle the Event Horizon Telescope will look at the accretion disk of Sagittarius A*? about just how close to edge-on we would be viewing any accretion disk around the ...
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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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If blackholes are spherical, what is the prespective of the blackhole image? [duplicate]

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 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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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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Have we seen a black hole?

Have we actually seen a black hole out there? By "seen" I mean "recorded a em-spectrum image of gravitational lensing caused by object believed to be black hole".
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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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Can magnetism escape a black hole?

I know light, and practically nothing but gravity can escape a black hole. My question is: can magnetism escape a black hole? A couple things that convince me it can are: Jupiter's magnetic field ...
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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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What can be learned from, or noted in this LIGO Orrery video?

The Ars Technica article Physicists detected gravitational waves from four new black-hole mergers notes that This brings the total number of events detected by LIGO and Virgo to 11. It also has a ...
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Why don't Neutron Stars form event horizon?

Trying to compare density of Black Holes and Neutron Stars I came up with the following: A typical neutron star has a mass between about 1.4 and 3.2 solar masses1[3] (see Chandrasekhar Limit), with a ...
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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 do Earth and moon move apart but binary black holes move closer?

According to the accepted answer on Is the moon moving further away from Earth and closer to the Sun? Why?, the moon is receding from Earth because tidal forces and friction cause energy to be lost. ...
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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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Where is the flaw in this hypothetical concept of escaping event horizon using another's blackhole flyby?

imagine two black holes approaching each other in a way that they will perform just very close flyby. You have a spaceship just below the event horizon of one black hole in line between centers of ...
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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 center ...
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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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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 center ...
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What type of energy is escaping from black-hole's poles?

Following this article, it is stated that: As a star drifts too close to a supermassive black hole, intense tidal stresses rip the star to shreds. As this happens, the shredded material will ...

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