All Questions
20
questions
7
votes
5
answers
6k
views
How can micro black holes exist?
How could a micro black hole exist, when there is so little matter to produce the intense gravitational force required to crush matter to that extent? It takes the collapse of a supermassive star to ...
- 393
0
votes
0
answers
46
views
Ejected bodies, dynamical friction and dark energy?
I have a question after reading a couple of papers (https://arxiv.org/abs/1707.06220 and https://www.arxiv-vanity.com/papers/1102.0007/).
Here, the authors seem to indicate that when bodies like stars ...
- 2,462
1
vote
1
answer
70
views
Why is a primordial black hole's mass of the same order as the horizon mass in the early universe?
I am reading a paper on primordial black holes (PBHs), and it says that PBHs should form during the first second of the universe with masses of the same order of magnitude as the horizon mass.
I ...
- 555
2
votes
2
answers
106
views
Does the rate of expansion of the universe depend on the mass or size of the galaxies?
Does the rate of expansion of the universe depend on the mass or size of the galaxies? How constant dark energy density affect the massive/lighter galaxies?
- 91
1
vote
1
answer
108
views
Are there Black Holes that do not have global time-like killing vector fields?
Can there be any Black Holes that do not have global timelike Killing vectors? And if there can be such Black Holes, does the conservation of energy apply to them? Can there be Black Holes with a non-...
- 2,462
1
vote
1
answer
441
views
How does a black hole have a magnetic field? [duplicate]
If a black hole is defined as an area where gravity is so great, it has a theoretical escape velocity that is faster than the speed of light. So how, since the carrying particle of magnetic force is a ...
- 11
8
votes
1
answer
859
views
What fraction of the mass of all baryonic matter are black holes?
Is there a calculation of how much of the mass of baryonic matter is black holes, including supermassive black holes in the center of galaxies?
- 956
2
votes
1
answer
63
views
Are the LIGO and VIRGO results consistent with the black hole statistics predicted by cosmology?
Have LIGO and VIRGO recorded enough gravity wave events to cross-check the black hole populations predicted by astrophysics and cosmology?
Basically, we now have another experimental tool to verify ...
- 248
7
votes
3
answers
504
views
Why are primordial black holes considered non-baryonic? [duplicate]
A very important question that has been bugging me is why do people consider primordial black holes to be non-baryonic. I know that such a statement is then used to saying that they can be considered ...
- 178
1
vote
0
answers
39
views
How are black hole masses calculated from gravitational waves? [duplicate]
I would like to know what data is used from gravitational wave detections to calculate black hole masses and how.
Also, what else can you deduce from gravitational wave detections? What was the exact ...
- 11
1
vote
1
answer
104
views
When did the first black holes form?
How long after the big bang did the first black holes form? How can we determine the answer to this question?
- 121
0
votes
1
answer
67
views
What is the jet luminosity of this quasar (ULAS J1120+0641)?
In wikipedia I found that its luminosity is $6.3×10^{13}$ solar luminosities, but is that the luminosity of the jet itself or is that the luminosity of the entire system (the jet + the accretion disk) ...
- 1,137
1
vote
0
answers
31
views
How is it possible to have such massive black holes? [duplicate]
Recent observations discovered really massive black holes, up to $20-40$ billions Solar masses.
Now, according to an recent study and various computer simulations (I'm sorry, I don't have any ...
- 3,705
1
vote
1
answer
193
views
Infinite number of universes? Black holes are guilty? [closed]
I was thinking, if the space is infinite, what if there are infinite number of spaces, inside our universe? I mean, everyone knows that black holes exist, but nobody knows what happens when you get ...
- 135
4
votes
2
answers
421
views
Smolin on Cosmological selection and neutron stars
Regarding the cosmological selection hypothesis and testable predictions, Lee Smolin asserted the following:
"Smolin: I did make two predictions which were eminently checkable by
astrophysical ...
- 2,299