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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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, ...
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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?
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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 ...
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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 ...
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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.
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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 &...
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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 ...
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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 ...
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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 ?
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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?
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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 ...
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What mass does an evaporating black hole have when it's schwarzschild radius equals the Planck length?
I am referring to Hawking radiation and the decrease in mass of the black hole with time
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Can LIGO distinguish rotating and non rotating black hole collisions?
I am assuming two rotating black holes create gravitational waves as they collide.
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How far are we from a black hole? [duplicate]
As far as I know, the closest (object reasonably believed to be a) black hole to Earth is Gaia BH1 at ~1560 ly. But presumably most black holes are hard to detect and there are undiscovered black ...
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Could we detect dark matter by black holes gaining unexplained mass?
Dark matter is said to interact only gravitationally, so it won't commonly form black holes by itself. But if a black hole is already there, and dark matter encounters the event horizon, it should go ...
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can we fly a rocket past the black hole in the milky way? [closed]
Some information needed is facts about the black hole in a milky way.
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Question: Planet 9 a Black Hole [duplicate]
I had a shower thought.
"Is it possible that the mysterious 9th or 10th planet is in fact a small Black Hole"?
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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 ...
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Observable Speed of objects orbiting a black hole
This is a mostly hypothetical question and thought experiment, and I am aware of some aspects plausibility of it are open for debate. Also, this is Version 2 of the question, as the first question was ...
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What is the rotational speed of Sagittarius A*?
Sagittarius A* is the Milky Way's own supermassive black hole. Up till recently, I used to think that Sagittarius A* was a static black hole, i.e. It had no rotational speed at all.
But after doing a ...
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How was it established that central galaxy's supermassive black holes are responsible for existence of radio lobes?
According to Wikipedia:
https://en.m.wikipedia.org/wiki/Radio_galaxy
"A giant radio galaxy is a special class of object characterized by the presence of radio lobes generated by relativistic jets ...
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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 ...
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Does the orbital velocity of a planet affect its escape velocity from the planet surfaces?
I'm trying to write a hard sci-fi novel with good accuracy, but when it comes to astronomy, I'm a total amateur.
Here's my fictional planet that orbit a black hole information:
Star Mass = 10000 Solar ...
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How does metallicity reduce the likelihood of black hole formation?
Large stars collapse and if they are large enough form black holes. But the likelihood reduces with metallicity.
What mechanism facilitates this? I believe it has something to do with opacity and ...
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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 ...
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Do pop III stars undergo supernova or direct collapse?
Population III stars were the first stars to form. They are hypothesised as being very massive, i.e., > 100 M$_{\odot}$. My question regards how do these stars end their lives?
An old orthodoxy for ...
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How to understand the charge of a black hole [duplicate]
How can I understand the charge of a black hole?
We can understand the charge of elementary particles, like the charge of a proton or neutron. But what does the charge of a big object like that of a ...
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Do Schwarzschild black holes exist in reality?
Do Schwarzschild black holes exist in reality? I have searched answer for this question but am not fully satisfied. Everything in the universe, including planets, stars, and galaxies, is spinning. How ...
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Do black holes "store" ancient light?
The way I understand it, black holes have extreme gravity, and time moves more slowly in high gravity.
For outside observers, it would seem that time would stop at the event horizon.
Does this mean ...
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How do you convert an uncertainty quoted in dex to a 1-sigma uncertainty?
The black hole mass measurement uncertainties from this paper https://arxiv.org/pdf/2006.15150.pdf are quoted in "dex" and are said to be equal to 0.4 dex. I have seen from certain papers ...
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How to get started with computational astrophysics? [closed]
I am a graduate student working on high energy astrophysics, in particular, accretion onto neutron stars and my research is mostly theoretical. However, with the recent advances in observational ...
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Photon sphere in neutron stars
Just a simple question.
Has neutron stars photon sphere as black holes?
If the answer is yes, what is the radious and why?
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What does "spun out" mean? [closed]
In A Very Short Introduction: Black Holes by Katherine Blundell, the author noted that "Black holes are very messy eaters", and explained that saying:
It transpires that only a fraction (...
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What does "to within less than about thirty Schwarzschild radii" mean?
In A Very Short Introduction: Black Holes by Katherine Blundell, the author discusses the imaging of plasma jets at the center of black holes:
At 50 million light-years from Earth an object moving at ...
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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 ...
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Could primordial black holes explain the SMBH in the galactic centers?
If there were enough primordial black holes (with the right mass) they could explain dark matter. Could they explain the gargantuan monster holes in the center of galaxies?
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How would a balloon structure of a universe look if we collected all mass together in a small region?
Imagine a universe with an inflating balloon structure of spacetime. Matter is distributed uniformly.
Now somehow we manage to collect all matter together within a small volume. What would happen to ...
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What's the proper shape of a black hole?
When we observe a circle we see a different shape than someone moving with high speed relative to us. They see an ellipse. Still we say the proper shape of the object is a circle.
Now a black hole ...
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How does a black hole look like independently of coordinates?
Observing a black hole from far away, far it looks as if infalling matter accumulates on the horizon. If one falls in though, there is no horizon at all (or it always stays in front of you).
Which ...
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What does it mean that the radial coordinate becomes the time coordinate behind the horizon?
The time and radial coördinate change are exchanged with one another behind the black hole horizon. So even stating that it's happening behind the horizon is misleading. There is, as a figure of ...
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Is V616 Monocerotis the closest black hole?
Now that HR 6819 has been found not to be a black hole after all, does that currently leave V616 Monocerotis as the closest known stellar mass black hole?
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How can we see black holes collapse if time inside the event horizon is infinite?
My understanding is that if you fell into a black hole, i.e. crossing the event horizon time would be speed up infinitely fast. This means I could see my whole galaxy die, new blackholes develop and ...
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Is the center of our galaxy, the Sagittarius A* black hole a former star?
If a black hole comes from a dying star, do we have a record or proof that our galactic center was once a huge ball of burning plasma? I'm not an astronomy student.
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Why is the ring in this simulation of Sgr A* off center?
In the recent releases of images of Sgr A*, simulated versions of what they expected were included along side the actual images they were able to get. What confuses me about these simulated images (...
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Difference between NSBH and BHNS mergers
What's the difference between Neutron Star-Black Hole Merger (NSBH) and Black Hole-Neutron Star Merger (BHNS)? Are they the same names for the same events or is there any difference between them?
I ...
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Black hole magnification factor
Given a black hole of mass $M$ which has a distance $D_1$ to Earth and $D_2$ to a galaxy being magnified, what is the magnification factor?
And a follow-up question:
Does it magnify across the ...
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Is a black hole really a neutron star with a gravitational time dilation factor of 1.0
Here's why I'm asking.
The gravitational time dilation factor at the surface of a star or planet can be expressed as $$gr/c^2$$
In theory, the same equation should apply to the gravitational length ...
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Using Einsteinpy to plot the precession of a star orbiting a black hole?
I am currently trying to code the precession of a star orbiting around a black hole, the issue I am having though is that I have no clue what the values are and what they mean in the code, if anyone ...
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Doubt regarding size and shape of black hole images published by the Event Horizon Telescope (EHT)
The recent publications of the images of black hole shadow by the Event Horizon Telescope collaboration prompts us to study black hole images in more details. According to the no-hair theorem, the ...
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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, ...
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