In another thread, it was discussed that you need about 3 solar masses worth of material (some say 5 or 6 but the exact amount is unimportant to this thread) to create a Black Hole.
So, while we might be unsure what that amount is, is it in fact an exact amount? Like could an object (probably a star) be sitting on the edge of black hole creation, and a hydrogen atom floating by gets captured by the gravitational field of the object/star, gets added to it’s mass, and then pushed the entire object/star over into black hold creation?
I believe thats actually incorrect - there is no minimum amount of mass needed to make a black hole. What matters is density. If you compressed an apple to a small enough radius it would collapse to make a microscopic black hole.
What they probably meant is that beyond a certain mass, the objects gravity gets so strong it compresses itself to form a black hole. In this case, i guess adding mass to an object “on the edge” could mean it then collapses to a black hole. I don’t think a single hydrogen atom would create enough gravity to make a difference though.
A star that is in the last throes of its existence will collapse to the object that its mass dictates. It will become a dwarf star, a neutron star, or a black hole. But this is the outcome of a long process of events. It doesn’t just suddenly happen as the result of the passing of a threshold.
It’s commonly held that for a black hole to naturally develop as part of a star’s life-cycle, the star must have greater than 40 times the solar mass of our sun and the black hole be formed as part of a supernova.
As much as this is the standard theory, I keep reading here and there cites of less than 40 solar masses. However, these citations of <40sms are never accompanied by a description of the mechanics (supernova) or the math to justify a <40sms claim.
Now, a black hole created by a supernova of a star >40sms can eventually loose mass through Hawking radiation and wind up with <40sms. But I’ve yet to see the math done to show how a <40sms star can naturally form a black hole.
I doubt that you could literally come within a single atomic mass of the threshold, and stay a neutron star: At that point, quantum fluctuations would probably be enough to push it over the edge, and once the hole forms, it ain’t going back. There’s also a bit more to it than just the mass: The temperature and pressure would also be relevant, but I’m not doing the math right now.
Obviously if a certain mass is contained in a certain area so that it’s escape velocity becomes the same as the speed of light you will get black hole formation, so in theory one atomic mass could push it over the edge, there is no limit on the size or mass (though they of course are directly related) theoritically for a blackhole (obviously quatum considerations excepted, as a small one will evapourate very quickly).
Actually in the other thread I was doing someresearch and it seems a star needs to be about 25 solar masses before it is a candidate for creating a black hole. 40 solar masses would certainly allow for black hole creation but 25 seems to be about the minimum.
I think mooka hit on the relevant aspect for this thread that some athers have called into question. You might get an apple to form a black hole with some help but it will not do it of its own accord. I think the OP wants to know about how much mass you need before that mass spontaneously forms a black hole due to its own gravitational attraction.
And I’m still going to say that’s roughly 3.2 solar masses. I’ve found nothing anywhere to tell me it’s going to be significantly different than this value.
Typical values for observed black holes in the Milky Way are 8-15M, you have to remember most of the mass is ejected when the star goes super nova. A neutron star can have a theortical maximum mass of 4M and a realistic maximum of 2M.
50M for the weight of a star is the rough limit for necessary black hole formation, though the precise limit is unknown. Smaller black holes could of been formed when the universe was very dense if there was enough variuation in the density. Hawkins radiation isn’t going to have much effect on a black hole of 40M (or indeed any but the smallest black holes).
A neutron star will collapse on its own if it’s above the so-called Oppenheimer-Volkoff mass, 3.3 M[sub]SUN[/sub], sure. In reality, though, there are a lot of reasons that gravitationally-bound objects more massive than that won’t collapse. Galaxies, for instance, are gravitationally bound.
A 3.2M star just isn’t going to form a black hole if that’s what your inferring, but if, as I think you are, saying that 3.2M is the minimum mass of a black hole formed by stellar collapse that sounds about right.
Anyway, the ratio for a Schwarzchild balck hole between it’s mass and it’s radius is:
m/r = (c^2)/2G
As you can see there is no theortical limiting factor on the mass as long as the mass is contained within a small enough region.
Good grief Q.E.D…I’m not arguing with you…I agree. The black hole may be as small as 3.2 solar masses once it is formed but the originating star needs to be MUCH larger. The vast majority of the star is expelled in a supernova such that you need a huge enough star to allow for the 3.2 solar mass limit to be left behind after it is done exploding.
You have two things at work here. The originating star’s mass and the mass of the remaining black hole. Again, the originating star needs to be about 25 solar masses to leave behind enough material for the smallest of black holes. The smallest black holes can be just a bit more than 3.2 solar masses as a neutron star can’t be bigger than 3.2 solar masses (add more mass and the neutron star is no longer stable and it will collapse into a black hole).
Fair enough but I’ll stick wioth my cite as the more reliable one. They certainly seem to have better credentials for this info than an unnamed text book of unknown age.
Yes, and all of those reasons have to do with other forces acting in opposition to gravitation, such as the cetrifugal force keeping galaxies from collapsing, or the thermal pressure keeping high-mass stars from collapsing.
Originally I was arguing with you but I was confusing the initial mass of the star with the final mass of the black hole. As the thread progressed I realized what you were saying, read the evidence provided and recognized my mistake and accept the results. I try (but not may always succeed) in allowing myself to be swayed from a position I initially held if the evidence says otherwise. It seems to me to be the point (or at least one of the points) behind this message board.
Before someone points this out as an apparent inconsistency I was arguing with Q.E.D. in the other thread. By the time I started posting to this thread I was in agreement with Q.E.D.. So, the first quote refers to this thread and the second quote refers to the other thread.
Slightly off-topic, but I bet it would be spectacular to watch a neutron star collapse into a black hole. Surely there would be a massive energy release during the process of collapse.
Okay, Q.E.D., I still don’t get where you’re coming from. I agree that a neutron star greater than 3.3 M[sub]SUN[/sub] will collapse to a black hole. I am not convinced that the same is true for a 3.3 M[sub]SUN[/sub] molecular cloud, or rocky body, or rubber band ball. These things use the electrostatic force to oppose gravity; do you discount this because it’s some force acting in opposition to gravity? I know that there’s some mass at which gravity will overcome the electrostatic force, but how do you know it’s less than 3.3 M[sub]SUN[/sub]? For a given mass object, you can make the surface gravity arbitrarily small by decreasing the density (stretching it out).
