My understanding of black holes is not complete and I am definitely missing something. Please clear this up for me if you can. I realise that it is denser, but I thought gravity depends on mass, not density.
Thanks.
2006-12-07 20:42:11 · 10 answers · asked by Nick 1 in Science & Mathematics ➔ Astronomy & Space
You're right - mass is the issue, not density, and the gravitatational pull of a black hole is no stronger than its progenitor star. But, the black hole is a lot smaller than the star, so it's possible to get a lot closer to it. Gravity obeys an inverse square law, so if you get twice as close the pull is four times stronger.
If, by some miracle, the sun suddenly turned into a black hole, the Earth would carry on orbiting as if nothing had happened.
2006-12-07 21:02:29 · answer #1 · answered by Iridflare 7 · 3⤊ 0⤋
Main-sequence stars with masses larger than 25 MSun become supernovae, leaving
behind a core that is more massive than the neutron star, about 3 MSun or more.
Therefore the gravity is higher, and can overcome the degenerate neutron pressure,
and the mass collapses to a black hole. The laws that apply inside a black
hole remain unknown, yet it is clear that the escape velocity from the vicinity of
these extremely dense objects must be very high, and possibly higher than the
speed of light. Recalling the escape velocity equation (Chapter 1), and setting
c ¼ ffiffiffiffiffiffiffiffiffiffiffi 2GM
d r
d ¼
2GM
c2
Within this distance (the Schwarzschild radius), nothing can escape the gravitational
influence of the black hole.
HAVE BLACK HOLES BEEN OBSERVED?
We have seen stars in binary systems, where we can observe only one star, and it
behaves as though it has a companion of a few solar masses. These systems are
also strong sources of X-rays. There are about half a dozen of these in our galaxy,
and these are possibly locations of remnants of massive stars which have become
black holes.
We observe the centers of galaxies (including our own) as huge sources of Xrays.
Astronomers can observe the speed of rotation near the center (from the
Doppler shift), and therefore determine the mass within the orbits (from the
circular velocity equation). This density is too high to be anything but a black
hole.
2006-12-07 22:44:08 · answer #2 · answered by amir_amaturastro 1 · 0⤊ 0⤋
In General Relativity, gravity depends on "stress-energy", of which mass is only a part. The energy of the gravity itself is a source of gravity. The equations are non-linear: the more gravity you have, the more source there is for gravity. So the mass of a black hole is larger than the mass of the star that formed it.
2006-12-08 01:48:04 · answer #3 · answered by cosmo 7 · 0⤊ 0⤋
imgagine space as a giant bed, if you set a bowling ball on it then things are likely to roll towards the bowling ball (excluding friction and all that fun stuff). Now take the mass of a bowling ball in the size of a marble and do the same. The indent will have the same depth, but the walls of the indent will be infinitely steeper. this is why a black whole has more gravity than a star
2006-12-07 21:27:46 · answer #4 · answered by Anonymous · 1⤊ 0⤋
The weight of the black hole inclines the space recline around it. If it depends on the mass then it could be that the mass of the hole has increased due to the forces that cause the hole to collapse.
2006-12-07 21:33:49 · answer #5 · answered by Anonymous · 1⤊ 0⤋
the denser the star is the stronger its gravity. if you have 2 stars, with the same size, but one of them is denser than the other, the denser star has a stronger gravity, or if you have a big star and a small and they have the same mass, the small star has a stronger gravity.
2006-12-07 23:40:15 · answer #6 · answered by Sam 1 · 0⤊ 0⤋
If you remained out at the surface of a star that shrank to a black hole the gravity where you were would stay the same.
If you followed the surface in as it shrank the gravity would increase accordingly!
2006-12-08 07:14:58 · answer #7 · answered by Billy Butthead 7 · 0⤊ 0⤋
i think it is to do with density, i.e: the more matter there is in a given space, the greater the density: lead can put more of itself into 1 cubic metre than marshmallow can, so the lead feels much heavier because the Earth is able to excert a greater gravitational pull on it; conversely proving lead excerts a proportional pull on the Earth greater than 1 cubic metre of marshmallow can. If, however, you were to condense an infinite amount of marshmallow into an infinitely small space, then you should have a black hole!
I
2006-12-07 22:07:23 · answer #8 · answered by darestobelieve 4 · 0⤊ 0⤋
simple answer: Its not stronger than the star it came from when that star first became a black hole. the way it does become stronger is by increasing its mass by sucking in more matter.
2006-12-07 22:55:37 · answer #9 · answered by llloki00001 5 · 0⤊ 0⤋
they're small- yet have an identical mass as a celeb. common regulations of physics do no longer look to maintain on with related to black holes so it really is theoretical how this takes position. look into "a short historic past of Time" by Stephen Hawking for a much extra perfect clarification
2016-11-24 22:40:23 · answer #10 · answered by ? 4 · 0⤊ 0⤋