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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Black hole explosion due to rotation [duplicate]

I am not an expert, I was just thinking about this scenario: A black hole that, for some reason, will start spinning faster and faster. Is it theoretically possible that the rotation becomes so fast ...
Nicola Lepetit's user avatar
3 votes
0 answers
137 views

Is there evidence against a Universe Black Hole?

As far as I know, the critical density of our observable universe coincides with the density of a huge black hole of the same radius. It could be a BH expanding at the speed of light and growing in ...
Juan Casado's user avatar
6 votes
2 answers
1k views

What are the most up to date, accepted, evolution stages of big stars that end in compact objects or a planetary nebula?

There are numerous charts and diagrams showing the stages of stellar evolution, as: or among many more (you can find several after googling a little), for example. When I studied my B.Sc. on Physics,...
omivela17's user avatar
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What would happen if a low-mass primordial black hole was captured by a brown dwarf or planet mass object?

Prompted by a recent PBS SpaceTime video The video in question discusses what would happen if a low-mass (asteroid-mass) primordial black hole were captured in the core of a Sun-like star (a so-called ...
asgallant's user avatar
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0 answers
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How long could a world like the Moon survive with an Earth mass black hole in the center?

I asked that question at the worldbuilding stack exchange. https://worldbuilding.stackexchange.com/questions/202273/how-long-could-a-planet-or-moon-survive-if-it-had-an-earth-mass-black-hole-withi ...
M. A. Golding's user avatar
21 votes
4 answers
6k views

What would happen if a small black hole fell into a star?

Let's say you created a cannon that can shoot small black holes and you shoot it at some star. Would the star just turn into a black hole silently? Or rather first destabilize and produce a last ...
Filip Sondej's user avatar
6 votes
1 answer
796 views

Could an hypothetical hidden black hole companion to the sun be revealed by proper motion data?

If the Sun were in a binary star system with a black hole companion, the Sun would be orbiting the black hole, and this should be reflected in a change in the observed proper motion of nearby stars. ...
tutizeri's user avatar
  • 357
-1 votes
2 answers
193 views

Why do we not call black holes black stars or dark stars?

I've never understood why the term black holes are widely used to describe what is actually a black star or dark star. I mean why name something just because of its extreme space curvature effects? In ...
eBookworm's user avatar
  • 135
2 votes
3 answers
271 views

How can Kerr black holes have a 'speed limit' to how fast they can spin?

Obviously, the speed of light is a presumed limit, at least for 'physical' objects moving 'within' ('through'?) spacetime, but... In recent news some scientists believe they have figured out the ...
Kurt Hikes's user avatar
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Can black holes even exist [if mass cannot be retained near the collapse threshold]?

A black hole happens because enough material mass exists in an area to create a gravitational field strong enough that nothing escapes (including light). This gravity also exceeds the strength of ...
hamstar's user avatar
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Amount of black holes over time

Hello the number of black holes is much bigger than the number of black holes in the past right?Let $b$ be the number of black holes in the universe.Obviously $\frac{db}{dt}>0$ but what about $\...
Root's user avatar
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2 votes
0 answers
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JWST Early Black Holes: Gas Collapsed To Metallic Hydrogen Core?

I was reading an article about early black holes found by JWST at Redshift 9. And saw that there was wonder at how large amounts of gas could collapse into a black hole as a theory. So my question is ...
WiFiSunset's user avatar
10 votes
2 answers
605 views

Are gravitational waves emitted equally in all directions?

I have a question regarding gravitational waves that I can't figure out. Hope some wise minds here can help a simple amateur without technical or scientific education. Two black holes rotating around ...
Peter's user avatar
  • 381
2 votes
1 answer
118 views

Black hole collision

In a situation where 2 black holes are close to colliding, but do not collide, can one black hole free/steal matter from the other in passing if the event horizons brush?
Shaun Eric Ewing's user avatar
23 votes
3 answers
3k views

From an outsider's perspective, how can a black hole grow if nothing ever crosses the event horizon?

Due to time dilation, an outside observer never sees a falling object actually cross the event horizon. I'm not referring to the optical illusion of red-shifted light making objects appear to fade ...
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2 answers
133 views

Possibility for black holes having negative energy

new to the community here. The question I have is whether black holes can possibly contain negative energy of any sort? It’s not a carefully thought-out question as space is not my bailiwick.
Bill Joe's user avatar
3 votes
4 answers
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How do stars 1 billion times the volume of our sun form and can they become black holes?

UY Scuti is a star 1 billion times the volume of our sun. A billion solar mass black hole formed 750 million years after the Big Bang. Could it have formed from a star like UY Scuti? Rare black hole ...
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7 votes
2 answers
3k views

Is there a limit to the Schwarzschild radius?

The Schwarzschild radius is a way for us to calculate the extent to which something has to be shrunk in order for it to become a black hole but I was wondering is there a limit to the object that we ...
Shubhankar Dixit's user avatar
1 vote
1 answer
97 views

Death of a Black Hole ≠ Rebirth?

So we all know that Stephen Hawking proved that Black Holes do evaporate overtime through hawking radiation. But that energy is released in very discrete amounts and there will be a time in the ...
Shubhankar Dixit's user avatar
0 votes
1 answer
111 views

Will an overspun black hole be white?

I recently watched a Kurzgesagt video about destroying black holes. In the video, they mentioned that you can (theoretically) "overspin" a black hole to remove its event horizon, thereby ...
Seggan's user avatar
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5 votes
1 answer
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What is a "Gentle Giant" Black Hole?

I have seen articles about the Milky Way's "gentle giant" black hole. For example: https://nypost.com/2022/05/12/image-of-gentle-giant-black-hole-at-milky-ways-center/ https://www.reuters....
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Question about how it's possible for black holes to have gravity and a possible resolution [duplicate]

1. Assumptions 1.a: gravity propagates at c (maximum) 1.b: gravitational fields cause time dilation 1.c: escape velocity at the event horizon is c 1.d: gravity "warps" space-time, but in ...
P Varga's user avatar
  • 190
1 vote
1 answer
290 views

The event horizon of a black hole

According to https://www.nationalgeographic.com/magazine/article/black-holes-einstein-star-eaters', when something crosses the event horizon of a black hole "A person watching from the outside ...
Ph1ra's user avatar
  • 13
9 votes
1 answer
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If you were on a planet orbiting a star that has a black hole companion, could you see light from your host star bent 180 degrees?

I realize that there is a distance from a black hole where photons can orbit. I understand that this orbit is very unstable, but I am concerned with photons just outside this range. Could the black ...
Jack R. Woods's user avatar
1 vote
0 answers
74 views

Could both the high incidence of supermassive Black Holes (BH) and the expansion of the universe be consequences of vacuum entanglement energy?

The notion that spacetime may emerge from entanglement between factors comprising a Hilbert space decomposition of the vacuum has been suggested by many (for example, M. Van Raamsdonk “Building up ...
RalphW's user avatar
  • 33
4 votes
2 answers
173 views

Is it possible to detect gravitational lensing of both light and gravitational waves originating from the same event?

Is it theoretically possible to detect gravitational lensing of both light and gravitational waves, when both originate from the same source/event (merger of two stellar black holes or merger of two ...
Alex's user avatar
  • 681
3 votes
1 answer
95 views

Could the revolution of super-massive black holes around each other create a pulsar-array gravitational wave signal despite 'final parsec' problem?

Some commentators on the recently-observed very-long-wavelength gravitational wave signal involving pulsars, like Dr. Becky Smethurst, have implied that it might not be merging supermassive black ...
Kurt Hikes's user avatar
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0 votes
1 answer
98 views

How do primordial black holes are able to have an event horizon?

How do primordial black holes have an event horizon? Sorry for the stupid question, but I know primordial black holes have just a handful of mass in a cosmic scale compressed in a singularity. But if ...
Artur Carneiro Barroso's user avatar
10 votes
2 answers
2k views

What is the mechanism through which mass is converted to thermal energy in the accretion disc of a black hole?

In the book The Cosmic Perspective, it is stated that as matter is falling into a supermassive black hole, up to $40\%$ of its mass are converted to thermal energy, making the accretion of matter ...
Vercassivelaunos's user avatar
19 votes
2 answers
3k views

Could we (Earth, Humanity, Solar System) be falling into a black hole?

With the expansion of the universe, all objects far away from us appear to be moving away (ie: exhibit Redshift). With distance, this acceleration / redshift also seems to increase (~73,000 (m/s) / (...
G. Putnam's user avatar
  • 299
2 votes
1 answer
114 views

Can a quasi-star develop a stable crust?

Could a quasi-star potentially develop a stable outer layer or crust during its early stage of formation if it were to be bombarded with substantial amounts of matter, coexisting with its core and the ...
Sandro Kakhetelidze's user avatar
0 votes
1 answer
98 views

Could You Escape an Event Horizon by increasing a Black Hole's velocity?

I have an idea for trying to escape the black hole's event horizon that might make basically no sense and I want it double checked. Basically, I do know that you can't escape the event horizon unless ...
skout's user avatar
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1 vote
1 answer
206 views

Will the Sun fall into a black hole? If so, when and which one?

According to the Wikipedia page "Timeline of the far future", stellar remnants not ejected from their galaxies will fall into the central supermassive black holes over a time scale of around ...
qdinar's user avatar
  • 145
4 votes
1 answer
958 views

Which wavelength is most likely to be emitted over the lifetime of a black hole by hawking radiation and which is most likely at any given time?

What equations tells us the most likely wavelength emitted for a given black hole mass at any instant in time and over the whole life of the black hole?
user avatar
1 vote
1 answer
117 views

Do black holes emit dark matter as Hawking radiation?

When a star made from protons neutrons and electrons becomes a black hole that black hole can emit protons neutrons and electrons as Hawking radiation. Dark matter is unusual matter: is there any ...
user avatar
3 votes
1 answer
85 views

Angular size of an object falling into a black hole

People often say that an object freezes over a black hole’s event horizon as it falls in. This is because only a finite amount of proper time passes for the object before it crosses the event horizon. ...
Larry_Boy's user avatar
0 votes
0 answers
51 views

What is the force that drives electrons along the magnetic filaments of galaxies?

"Milky Way's mysterious filaments have 'older, distant cousins'" https://www.techexplorist.com/milky-ways-mysterious-filaments-older-distant-cousins/54966/?amp=1 Quote from article: "...
user avatar
1 vote
0 answers
49 views

Does the (relative) distance of the photon sphere from the center of a black hole vary according its mass?

I know that the photon circle or photon sphere is located at around 1.5 times the radius of the Schwarzschild event horizon, but wouldn't it be comparatively further out for smaller black holes? After ...
Kurt Hikes's user avatar
  • 4,927
6 votes
1 answer
545 views

What do the symbols signify in Dr. Becky Smethurst's radiation pressure equation for black holes?

In her most recent video, "An ULTRAMASSIVE black hole has been discovered in a BRAND NEW way!", as well as a previous video, "How massive can black holes get?", Dr. Becky Smethurst ...
Kurt Hikes's user avatar
  • 4,927
0 votes
0 answers
45 views

BH rotating at maximum speed and extremal BH

Academic problem: What should be the rotational speed of a planet at the equator such as there is no surface gravity? Plugging centripetal force=gravitational force... $$mv^2/R=GMm/R^2$$ we get, ...
riemannium's user avatar
2 votes
1 answer
171 views

What is the maximum radius of a pure iron-56 planet?

Suppose we are building a pure iron-56 planet atom by atom, how large can it get in terms of radius before it collapses into a black hole?
EFanZh's user avatar
  • 123
1 vote
2 answers
137 views

What is the variation in the time it takes a black hole to evaporate from Hawking radiation?

I often see figures of how long it would take a black hole of a given mass to evaporate away due to Hawking Radiation. The wiki page itself mentions that a black hole of about $10^{11}$ kg takes ...
zibadawa timmy's user avatar
1 vote
3 answers
126 views

How does Very Long Baseline Interferometry work?

According to internet sources, this technique increases the effective diameter of the telescope, thus improving the angular resolution of the telescope. However I don't understand how this actually ...
Ambica Govind's user avatar
1 vote
1 answer
66 views

Would the influence of a black hole nearby cause a tilt of 63° of our solar system in relation to our galaxy?

I am trying to understand the influence of black holes and the tilts of solar systems on their axial plane In relation to the plane of their host galaxies.
Ashtaras's user avatar
4 votes
1 answer
116 views

Do collisions of stars still undergoing fusion reactions produce gravitational waves?

When studying gravitational wave sources, we just consider BNS, NSBH, and BBH systems since their inspiraling and collisions can produce detectable graviational waves. Also according to the paper &...
noob anomaly's user avatar
7 votes
2 answers
3k views

How do two black holes merge?

Since at the Event Horizon, time stops completely, how do two black holes merge together? Shouldn't they should stop moving due to time dilation when they get closer to each other's Schwarzschild ...
Shounak Das's user avatar
6 votes
4 answers
1k views

How is it possible to have black holes in the sub-atomic scale?

I've heard of black holes forming in particle accelerators. This was a huge topic of discussion back in the early '00 with the grand experiment in CERN to prove the Higgs boson. Many people started ...
Demis's user avatar
  • 883
3 votes
3 answers
230 views

Viewing black holes?

How could you possibly see a black hole when there are stars etc in front of it and then the matter being drawn into it , all you would view surely would be the objects in front of the black hole ?
Big4's user avatar
  • 55
2 votes
0 answers
45 views

Is frame dragging expected to be quantized in a theory of quantum gravity?

Protons and electrons have angular momentum which is quantized. Would the angular momentum of black holes be quantized in quantum gravity? Would this then affect Hawking radiation?
user avatar
1 vote
2 answers
163 views

Why do black holes grow?

I'll use the term 'understand' here. By that, I mean that I understand in laymen's terms. From my questions, it should be obvious that I don't understand mathematically. I understand how black holes ...
Software Engineer's user avatar

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