Questions tagged [black-hole]
Questions regarding points of extremely high mass density, which creates an extremely strong gravitational field from which light cannot escape.
58
questions with no upvoted or accepted answers
10
votes
0
answers
181
views
How well conserved is etendue in extreme gravitational lensing scenarios?
This excellent answer to Could dark matter exist in the Universe in the form of sufficiently dense objects? includes the following image and description:
Light from the background galaxy circles a ...
- 31.4k
9
votes
0
answers
196
views
Why would a black hole have a disk, but not emit x-rays?
There's a recent paper in Nature about LB-1, a B-class star orbiting a massive black hole.
I don't understand how these two parts of the paper can be reconciled. On page 2, the authors argue that the ...
- 3,992
6
votes
1
answer
288
views
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 ...
5
votes
0
answers
86
views
Time dilation if an asteroid and a small black hole entered a larger black hole?
For an outside observer, everything moves slower the closer it is to a black hole's event horizon, even photons, due to the black hole's time dilation.
We also know that when two black holes collide, ...
- 151
5
votes
0
answers
52
views
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 ...
- 1,022
5
votes
0
answers
166
views
Can primordial black holes be found orbiting other stars?
A recent study suggests a that a primordial black hole may be orbiting the sun at and that they can be common near other star systems.
What measurements and equipment can perhaps find BH's near ...
- 4,188
5
votes
0
answers
178
views
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 ...
- 1,399
4
votes
0
answers
76
views
Do all black holes, including stellar-mass ones, rotate at nearly the speed of light? Also, what exactly does that do to their shape?
From what I understand, astrophysicists have known for almost a decade that supermassive black holes seem to spin at incredible velocities; nearly the speed of light... In fact, some of the outer ...
- 4,891
4
votes
0
answers
50
views
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 ...
- 141
4
votes
0
answers
64
views
Charged black holes selective eaters
We have a charged black hole which is negatively charged. For this simple case the black hole is not rotating.
If a negatively charged particle approaches the singularity the electromagnetic repulsion ...
- 355
4
votes
0
answers
83
views
Why does the outside edge of a Kerr black hole ergosphere rotate at the same speed as the inner edge?
Reading through the Wikipedia on a Kerr black hole ergosphere, and this nice question on the maximal spin rate of a black hole leads me to ask: why does the outer edge of the ergosphere rotate at the ...
- 1,556
3
votes
0
answers
67
views
Could we see small objects like animals on an exoplanet using Solar Gravitational Lensing (SGL) if we could use any star or a black hole for lensing?
Theoretically, if a telescope is positioned in a focal point of a supermassive black hole or a star much more massive than the Sun, would there be a limit to how far away an observable planet can be ...
- 31
3
votes
0
answers
62
views
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 ...
- 1,022
3
votes
0
answers
48
views
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. ...
3
votes
0
answers
55
views
What fractions of matter are retained and displaced by quasars?
Following on from a query concerning quasar mass, what fraction of matter is ejected compared to matter that is lost to the BH?
Is there a graph that describes the fractions of the mass of quasars ...
- 4,188
3
votes
0
answers
345
views
How does the size of a naked black hole effect its photon sphere?
What effect does the size of a black hole have on the size or density of the photon sphere and it's proximity to the horizon?
For example: A person is in space looking at 2 black holes, one of them ...
- 1
3
votes
0
answers
54
views
Can we resolve the centers of Milky way's satellite galaxies now?
Two dwarf satellite galaxies of our galaxy have large $\frac{\text{diameter}}{\text{distance}}$ values. And one of them, Canis Major Dwarf, is 8kpc away which is
the same with our distance to the ...
- 3,063
2
votes
0
answers
76
views
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 ...
- 21
2
votes
0
answers
65
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 ...
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?
user48394
2
votes
0
answers
434
views
Is the three-year delay of the AT2018hyz event related to time dilation?
According to LiveScience,
Astronomers have spotted a black hole mysteriously spewing up chunks of a devoured star several years after consuming it.
The event, which scientists have classified as ...
- 191
2
votes
0
answers
106
views
In what year (2014?) the gravitational wave triggered by this merger was possibly generated?
Re: "A transient radio source consistent with a merger-triggered core collapse supernova"
https://www.science.org/doi/10.1126/science.abg6037
Actually the described merger consisted of two ...
- 681
2
votes
0
answers
38
views
Could we detect a globular cluster consisting entirely of black holes?
A paper recently came out in Nature simulating the evolution of the $\sim10^4M_{\odot}$ globular cluster Palomar 4 (Gieles et al. 2021, arXiv link). The authors argue that in ~1 billion years, a ...
- 36k
2
votes
0
answers
81
views
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?
- 1,548
2
votes
0
answers
60
views
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, ...
- 323
2
votes
0
answers
85
views
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 ...
- 41
2
votes
0
answers
100
views
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 ...
2
votes
0
answers
97
views
If Planet Nine is a primordial black hole could it explain 'Oumuamua and Borisov's orbits without them being interstellar?
There has been an increasing amount of interest in the possibility of primordial black holes and that Planet Nine may be one itself. Planet Nine is a potential explanation for the orbital ...
2
votes
0
answers
55
views
Is there a way to calculate how much damage black hole merger shockwaves inflict on nearby objects?
Black hole mergers lose respective rotational energy during a merger. I understand that the energy 'emitted' is scattered as gravitational 'energy' that can henceforth be detected by gravitational ...
2
votes
0
answers
95
views
Can we determine where the north and south magnetic poles are on stars and black holes?
The question is related to this about Are there collected data about the direction of rotation of black holes and the direction of the magnetic field?. Perhaps it is observable for pulsars?
- 241
1
vote
0
answers
72
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 ...
- 23
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 ...
- 4,891
1
vote
0
answers
52
views
How do I estimate the number of neutron stars and black holes relative to the number of stars in the main sequence and white dwarfs?
Recently, I had a homework question that gave me the mass of a main-sequence star, that is, M_tp = 0.9 M_solar, and the population formed at the same time. I am supposed to use the stellar birth ...
- 41
1
vote
0
answers
103
views
Could "gravitational atom” black hole be detected using observation of gravitational microlensing?
D. Baumann et al., published the article hypothesizing existence of "gravitational atom” black holes (not sure whether those are just stellar ones or also those could be supermassive black holes ...
- 681
1
vote
0
answers
134
views
How did the Universe climb out of its own Big Bang black hole?
The Big Bang started as a singularity. That means small. All the matter in the universe was in a volume smaller than its own Schwarzchild radius. The universe was inside a black hole.
At present, the ...
- 930
1
vote
0
answers
50
views
Has the Advection-Dominated Accretion Flows (ADAF) model been used to describe accretion flow around a rotating black hole?
I am studying Advection-Dominated Accretion Flows (ADAF) from the review paper Advection-Dominated Accretion around
Black Holes. In section 2.1 of the paper, the authors provide the basic equations of ...
- 323
1
vote
0
answers
95
views
What happens inside a massive collapsing shell?
I have already asked this on the physics site. I am not sure where it fits better.
Consider a massive spherical shell collapsing under its own gravity. Say the mass is that of one galaxy. The ...
user42560
1
vote
0
answers
89
views
What is a typical "pulse rate" for a black hole "heartbeat"? Is the process better understood than it was in 2011?
The 2011 NASA Goddard video NASA | RXTE Detects 'Heartbeat' Of Smallest Black Hole Candidate mentions a heartbeat and includes a graphic of pulses from GRS 1915+105. A screenshot is shown below. No ...
- 31.4k
1
vote
0
answers
64
views
Can the other side of the observable universe be seen as a black hole?
When looking at the objects near the horizon of the observable universe, the objects seem to emit radiation that is red-shifted. Time seems to advance at a slower rate than our own and at the horizon ...
1
vote
0
answers
65
views
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 ...
- 31.4k
1
vote
0
answers
61
views
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 ...
- 111
1
vote
0
answers
80
views
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 ...
- 5,526
1
vote
0
answers
66
views
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 ...
- 31
1
vote
0
answers
121
views
What is the Schwarzschild radius actually?
I am currently writing a detailed essay about black holes, the history of their discovery and their characteristics and I can't find the appropriate literature online and in my local libraries (I even ...
- 11
1
vote
0
answers
66
views
Does the spin rate of a black hole correspond to a physical feature?
If the mass and orbital period for two neutron stars is known before collapse to a black hole and the rate of spin is known after collapse, 100 revolutions per second for instance, that will correlate ...
- 73
1
vote
0
answers
53
views
Causes of emission of accretion disk
As far as I can see, there are two main sources for the emission of energy from an accretion disk:
release of gravitational potential energy of the infalling matter;
friction from differential ...
- 2,404
1
vote
0
answers
137
views
How does a spinning black hole affect space-time compared to a non-spinning black hole?
I often see questions on this site that only apply to non-spinning black holes and often wonder how the answer would be different for a spinning black hole. As the title says, what are the major ...
- 813
1
vote
0
answers
35
views
How accurate are the new visualisations of V404 Cygni
A number of pictures and some animations similar to the ones below have had much press recently. Clearly the colours are artificial, but I wondered how accurately the represent the geometry of the ...
- 10.2k
1
vote
0
answers
515
views
Does the Canis Major Dwarf Galaxy have a black hole at its centre?
I am just wondering: is there a potential galactic centre out there that's very close to us? I know that CMDG is irregular, but can it still contain a black hole at the centre?
- 285
1
vote
0
answers
130
views
The black hole binary that was detected by advanced LIGO - how do such hypergiant binaries form?
With today's announcement of the historic detection of gravitational waves from the merger of 36 solar mass and 29 solar mass black holes 1.3 billion light years away, one can not help but wonder how ...
- 373