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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Do black holes have “age” when they form?

I was thinking about black holes, and I know that they form by the death of massive stars. I was wondering, though, do they technically have an "age" when they're born? Do they begin at 0 ...
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What is Lawrence Krause's theory of total energies?

Does Lawrence Krauss theory say that the total energy in the universe is equal to zero or that the energy in the entire universe remains constant and the mass in the entire universe also remains ...
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Would a possible accretion disk around a primordial black hole 500 au from the Sun be visible in present telescopes?

If the hypothetical two-inch black hole 500 au from the Sun had an accretion disk, might current telescopes detect it already or do we have to wait till the Vera Rubin Observatory starts work?
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Do the orbits of 14 TNOs even need an explanation (a planet mass) or is it just for historical reasons (how they formed)?

From Uranus' orbit we concluded there must be another planet beyond Uranus, eventually discovered and named Neptune. The same happened when Pluto was about to be discovered (though on false premises). ...
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Understanding various conditions where a star and a black hole meet and there is no tidal disruption; what all can we infer from this diagram?

Can an entire star pass through the event horizon of a black hole unharmed? is a one sentence HNQ with an amazing (to me at least) answer: for supermassive black holes larger than roughly 100 million ...
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Can an entire star pass through the event horizon of a black hole unharmed?

Can there be any black hole big enough that a regular sized star can pass through its event horizon unharmed?
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If the spacetime singularity at a black hole's event horizon is an artificial one then how can it be real?

If the metric belonging to the spacetime of a black hole is expressed as the Schwarzschild metric, it turns out that there is a coordinate singularity at the event horizon. If we use an alternative ...
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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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If a black hole has the same mass as me, then why dont i suck everything at my center of mass?

So, a black hole is very dense that you can get really close to its center of mass that it has a strong pull, well, if i have the mass of a black hole that has a really small event horizon, why doesnt ...
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If a black hole has a mass similar to a star, why does it have a different gravitational pull?

Say there is a black hole with 1 solar mass, having the sun's mass, it would have the same gravity as the sun, right? But it still has an event horizon, so why does it have such a strong gravitational ...
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How do we know that supermassive black holes can gain mass by means other than merging with other supermassive black holes?

I just stumbled across the following answer "update" from 2013: This just in, recent observations have ruled out the possibility that SMBHs gain mass only through merging with other black ...
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Is there anything different about the gravitation around a non-spinning black hole and a neutron star of the same mass?

If we perform a simple experiment by orbiting identical spacecraft around a non-rotating black hole and a non-rotating neutron star of equal mass at a "safe" distance, and ignore differences ...
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Can Newton's gravity equation explain why black holes are so strong?

I was just wondering why black hole's gravitational forces are so powerful. I know it's usually explained by Einstein's relativity which states that when an object becomes infinitely dense (a compact ...
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What is Hawking radiation? [closed]

Like the radiation the Sun gives out to sustain it's circular shape, will Hawking radiation sustain the black hole's shape?
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What is the Inner Horizon of a rotating black hole?

My understanding is that any object with non-zero angular momentum which undergoes gravitational collapse to a black hole will become a rotating black hole. In reality all black holes will be rotating ...
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Is the discovery of a “mass gap” black hole by this tiny telescope just plain luck/serendipity or could it be the first of many similar discoveries?

The Kilodegree Extremely Little Telescope is a pair of modest lenses with high quality medium format CCDs attached sitting on oversized mounts in Arizona and Sutherland. These very modest instruments ...
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Is it true that black holes emit only photons, electrons, and positrons in the form of Hawking Radiation?

According to this comment, if the peak photon energy is 511 KeV, electrons and antielectrons begin to be produced along with photons. So when the peak energy is ~940 MeV, the rest mass of a proton, ...
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What scales and types of EM and gravitational radiation do we expect to be given off by a black hole, in the final stages of evaporation?

In theory, black holes of all sizes eventually evaporate, due to quantum processes close to the event horizon that result in net emissions that appear to come from the black hole (but actually ...
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Does General Relativity predict anything about the creating of a singularity, once enough matter collapses inward to form an event horizon?

Ignoring quantum gravity, which we don't know much about, current theory (GR) states that an event horizon forms when there is enough matter/energy density to create it, and logically, a singularity I ...
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Why did astronomers believe most or all stellar black holes had masses no greater than 15 solar masses?

The so-called 'mass gaps' for black holes, according to theoretical models, are between 2-5 solar masses and 50 to 150 solar masses. (Actually, I have read that there is no good theoretical reason ...
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Can Hawking Radiation ever be detected and does it exist? [duplicate]

I'm researching black hole Hawking radiation for a contest, and so far I get the overall gist of how the process works. But as far as I've searched, there hasn't been any confirmed observational ...
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Is there a closest free-return trajectory to a black hole?

The scenario I am imagining is a test particle falling from infinity with an initial off-center velocity. In Newtonian mechanics the path would be a hyperbola. But I assume that, near a black hole, ...
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Does Hawking Radiation really exist and Why “negative energy” in virtual particles? [duplicate]

I'm doing some research on black holes for a science video contest - more specifically, on Hawking Radiation. As far as I know, there are these constant quantum fluctuations of "virtual" ...
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Could photons orbit a black hole if fired at the correct angle?

My experience with Kerbal Space Program gives me the impression that it's impossible to transfer from a stable orbit of one body to the stable orbit of another without deceleration. But is this true ...
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Does General Relativity really predict Black Holes?

I'm doing some research on black holes for a science video contest. I want to explain the physics of how they work, but also want to have a little background on how they're formed. As far as I've ...
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Is S2 still the fastest known star in the galaxy?

Wikipedia's entry for the star S2 says that it has the fastest known ballistic orbit, reaching speeds exceeding 5,000 km/s (11,000,000 mph, or ​1⁄60 the speed of light) and acceleration of about 1.5 ...
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What are detached black holes?

I understand what black holes are, and how they form, but I was recently introduced to the topic of detached black holes. What are they and how are they different from standard black holes?
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Can black holes be a subset of quark stars? If not, what are black holes made of?

Can stellar black holes be a category, or subset, of quark stars? Strange stars are so called not because they're weird (though they are) but because the extraordinary pressures within them should ...
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Astrophysical black holes deviating from Kerr black holes?

Rotating black holes are formed due to the gravitational collapse of massive spinning objects. And, it is generally believed that Kerr black hole solutions are valid for the empty space outside of the ...
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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) 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 and ...
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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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