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 do black holes form from stars that go supernova

I know that the cores of stars with more than 20 times the mass of the Sun collapse into black holes at the end of the star’s life. However, as far as my understanding goes, stars with cores that ...
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Can massive objects pull photons into existence?

When a photon tries to leave a black hole, it is redshifted until the wave length is infinite and the photon disappears(?). Could this also happen the other way round, that a (non existent) photon ...
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What are some challenging astrophysics problems for which we have data available? [closed]

I am a Computer Science student, and I would like to pursue a PhD in the same area, by applying artificial intelligence techniques to astrophysics. Not being an astrophysicist, however, I was curious ...
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Why are blackholes generally not considered as solid spheres with an escape velocity FTL?

I was reading Do Stars Vanish Into a Black Hole or Crash Against a Surface? A New Test Answers on space.com. It says the following: Another proposed alternative to event horizons is the "hard ...
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Medium sized Black Holes

For many years the existence of medium sized Black Holes (IMBH$^1$) have eluded scientists. BH of several times the mass of our sun have been found, as well as SMBH with millions of sun masses. SMBH's ...
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Can a Thorne-Żytkow object be the progenitor of a modern quasi-star?

I was reading some Wikipedia articles about astronomy, and came across an interesting line: The neutron star may also accrete sufficient material to collapse into a black hole. Now, here is my ...
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Can mass loss via accretion occur on stellar remnants?

We know that normal stars can lose mass to a binary companion. But can this happen to neutron stars and white dwarfs? Let's say a stellar black hole is being orbited by a white dwarf or neutron star. ...
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Can you escape a black hole by going into another (4th) dimension? [closed]

I imagine if there was a 2D black hole on a piece of paper, and something was inside the black hole had access to the 3rd dimension, they could just go "upwards" out of the black hole. Could ...
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Why don't black holes quickly eat up the galaxy/universe?

It's my understanding that the radius of the event horizon of a black hole is proportional to it's mass. Which means the surface area of a black hole is proportional to it's mass squared. Lets just ...
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Math for the “universe in a black hole” hypothesis?

There are various pop-science article entitled Are we living in a Black Hole? or Did A Black Hole Give Birth To Our Universe? which say things like There’s a lot to like about the idea that there’s a ...
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What is the relation between between hardness ratio(HR) and spectral state of a X-ray binary star system?

When reading about hardness ratio, it shows that depending on the hardness ratio spectral states of a binary star can be divided into soft, hard states. So how the HR value changes with respect to the ...
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Does photon capture in a black hole (or any other “very compact” object) reduce the luminosity/photon flux from its self isotropic emission?

I don't know if this is even a feasible question or if I have a point in asking so. Let's say we can model the radiation coming from a very compact object, such as a BH with an accretion disc or any ...
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Why does black hole draw off some mass from orbiting star instead of sucking it?

Researchers saw repeated outbursts — every 114 days, on average — in a galaxy some 570 million light-years away from Earth. Here outburst because of black hole draws mass off from the galaxy? Location:...
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Calculating the black hole evaporation time

Black holes evaporate very, very slowly by emitting Hawking radiation, and eventually they disappear, maybe even during the lifetime of the universe ($\sim 1.5 \times 10^{18}{\rm s}$). That's what I ...
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Stellar life cycle flow chart with mass conditions and time scales

I remember that in my nuclear astrophysics lecture a decade ago, our lecturer drew a large flow chart like diagram of stellar evolution in dependence of the mass of the star (in solar units) on the ...
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I need to study space, planets and black holes, how do I study them on my own [closed]

I need to study space, planets and black holes, how do I study them on my own, knowing that I am an Arab and I do not know English. I use translation applications. I speak with you. Can you help me ...
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Why are relativistic jets perpendicular to the accretion disk?

From looking at many images (artist's rendering and computer-generated) at black holes, I've noticed that the relativistic jets are always perpendicular to the accretion disk. Is this always true, and ...
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How does a galaxy in Abell 2261 exist without a black hole in the center?

Here a source says that astronomers looked for a black hole in the brightest galaxy in the cluster Abell 2261, A2261-BCG, but found nothing: However, X-ray observations from NASA's Chandra X-ray ...
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Astronomical resources helpful for creating an animation in the browser of the movements of an astronomical object in the sky?

Background I would like to create a website that shows an animation of the path of Sagittarius A* (or any other object in space) during one day for a specific location. So that the user can see where ...
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What came first: Galaxies or Stars? [duplicate]

In Stephen Hawking's A Brief History Of Time, the book mentions that "in regions that were slightly denser than average...galaxies were born." (pg 123). However, according to many other ...
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Why is there no color shift on the photo of the M87 black hole?

Last year, the first photo of a black hole in Messier 87 was published: (Source: EHT) It is quite obvious that about the lower half of the accretion disk is brighter. This question (or rather, the ...
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How big would the supernova when a neutron star collides with another neutron star? [closed]

If two neutrons stars that are orbiting were to collide, how big would the supernova explosion be? Would a new black hole or a new supernova remnant be formed?
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Is there any planet or black hole where we could experience time dilation like in the movie Interstellar?

As we seen in Interstellar movie Copper goes to a planet where he experienced time dilation which was 1 hour of staying on that planet will cost the 7 years on the earth. So, is there any planet or ...
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What if a primordial black hole went through the Sun?

How much mass would the Sun lose to a primordial black hole that (initially) has 10 Earth masses, passing through or close to the center of the Sun at solar escape velocity? How massive would the Sun ...
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Do neutron stars have an ergosphere?

Ergospheres are a property of black holes, and do neutron stars have it? If yes, why seldom article mentions that; if no, why can't neutron stars have this ergosphere component?
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Why is a black hole's Hawking radiation temperature inversely proportional to its mass/size?

As a black hole shrinks in volume and mass, shouldn't its temperature get lower? Shouldn't it evaporate more slowly? Naively, (very naively), I think that with a smaller surface area (as per its ...
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Why black holes look black to us?

Why black holes look black to us? The question might sound weird but my head stuck in it. As we know objects that fall into the black holes seem to remain unchanged in its event horizon due to the ...
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Would a black hole passing next to a star create a deadly focal point due to gravitational lensing?

Black holes bend all kinds of radiation thanks to their giant gravity. Now imagine that a black hole passes close to some star (we know of cases when black hole devours a star). Star emits massive ...
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Could all spiral-galaxies with black holes at their centers be connected via the BH themselves or Einstein-Rosen-Bridges?

If it's true that almost every spiral-galaxy has a black hole at its center, then I have this question. Could all these galaxies be connected via their black holes, or their Einstein-Rosen-Bridges?
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Why are event horizons described in Schwarzschild radii rather than diameters, and either way can they change equator to pole?

I never heard of Schwarzschild diameters, only of Schwarzschild radii. Why is it like this? Wouldn't it be better to portray the (possible) size of a black hole in a diameter? Either way, can we use ...
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What if the two Black Holes spiraling around each other are evaporating via their Hawking radiation?

A non-technical explanation In a Gravitational Wave event, the point is that in this event when Black Holes are spiraling around each other, they will cause the very fabric of Space-time to ripple and ...
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Is the angular size of the black hole in the movie “interstellar” completely overblown?

I assume everybody is tired of reading questions derived from the movie Interstellar, I will try to keep this short and simple: In general in movies, in order to have stunning visuals, celestial ...
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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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Why doesn't the black hole in the center of the Milky Way glow similarly to the famous M87 image?

The M87 image made some astronomers famous recently as the first image of a black hole. In the Milky Way, it has been concluded that there must be a black hole due to the movement of stars near the ...
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Will the Sagittarius A* Black Hole eventually swallow the entire Galaxy?

In one of his interviews, Sir Roger Penrose mentioned that when the Milky Way and the Andromeda galaxies eventually "collide" and merge into one, their super-massive black holes will also ...
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Can two singularities combine into one? [duplicate]

We know that black holes can collide and merge, but if they each have a singularity at the core, how can the two singularities merge and become one? Wouldn't the mere fact of a second singularity in ...
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Was our Universe born inside a Black Hole [duplicate]

Is there any possibility that our Universe was just born inside a Black Hole? If so, then mathematically prove that it happened and if it didn't happen, then please mathematically disprove it.
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How do dark stars form?

I'm not referring to a star made of dark matter or a Newtonian dark star. I'm talking about a star powered by dark matter annihilation. I imagine it would form close to the centers of galaxies where ...
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Black Hole Collision & Gravitational Waves

The Gravitational waves detected by LIGO on 14th September 2015 are attributed to a collision of two black holes, which had been rotating near the speed of light around each other just before the ...
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Does this black hole mass/galaxy stellar mass relation hold for extremely low-mass galaxies?

I read a preprint last week (Palmese & Conselice 2020) that suggested that the recent gravitational wave detection GW190521 could be the end result of a merger of two extremely low-mass galaxies. ...
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Catalogue of black holes

Where can one find a reliable list of black holes that have been discovered/observed so far, directly or indirectly, along with their properties, like mass, spin, etc.?
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Are black holes considered part of baryonic content of universe?

Are black holes (like those detected by LIGO, for instance) part of baryonic content of universe or part of dark matter? Why?
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What would happen on earth if there was a surge in gravitational waves [duplicate]

There are claims that when massive objects merge some of their mass is converted to gravitational energy. Such as the following links: https://astronomy.stackexchange.com/a/38727/2305 https://youtu.be/...
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GW190521 black hole merger total mass calculation and missing mass, how does this happen?

I have just read an article about that black hole merge event (it's in Italian): Sette miliardi di anni fa, due mostri si unirono What made me curious is that the article tell that a 66 solar mass ...
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Why isn't IMBH candidate GW190521 very “chirpy”? Which types of events will produce the most chirp-like behavior?

The first gravitational wave observations were noted for their "chirp-like" behavior; the objects would speed up as they got closer, radiating more strongly and therefore loosing energy ...
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How does hawking radiation work without virtual particles?

How does hawking radiation work without the existence for virtual particles? I read that certain quantum fields are distorted when a black hole forms on top of them. But what fields specifically? If ...
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How do accretion disks around black holes evaporate via winds?

I'm curious as to how accretion disks around black holes evaporate. I've heard winds play a crucial role in this. But what winds specifically and how do they form? Is it a stellar wind of sorts? If so ...
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How String Theory calculates the Entropy of the Black Hole in a Background dependent way?

How does string theory get an agreement to the Hawking-Bekenstein equations to calculate the quantum entropy of a black hole in a background dependent way? Is there any sort of area parameter in ...
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201 views

Can Axions escape the Black Holes?

I read about Tachyons and Gravitational Waves and also about Exotic matter, really nothing can escape a Black Hole, can Axions escape for providing a new hope?
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Black Hole - energy and matter

Can someone explain what is happening with energy (e.g. light) and matter which was collected by a black hole? I suppose that matter builds a black hole's mass and size, but what about light? Does it ...

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