Scientists Discover Teeny Tiny Black Hole

AbsoluteXyro writes "According to a Space.com article, NASA scientists have discovered the smallest known black hole to date. The object is known as 'XTE J1650-500'. Weighing in at a scant 3.8 solar masses and measuring only 15 miles across, this finding sheds new light on the lower limit of black hole sizes and the critical threshold at which a star will become a black hole upon its death, rather than a neutron star. XTE J1650-500 beats out the previous record holder, GRO 1655-40, by about 2.5 solar masses."

Re:15 miles across?

[imsabbel]

INfinite.

A black hole of any stelar size will only radiate like a body in the femto-kelvin range.

This means that galactic background radiation will "refill" it more than it could ever lose.

Re:The Earth in danger from microscopic black hole

[Anonymous Coward]

Another short story, well worth the 5 minutes it takes to read, is The Hole Man by Larry Niven. It has a pea-sized planet-gobbling black hole as a central part of the storyline.

http://www.danamania.com/tmp/holeman.txt [danamania.com] has a copy.

Re:Probably Something Stupid

[afaik_ianal]

That I don't fully understand (IANAQP), but this link [ucdavis.edu] gets me part of the way.

In short, and with suitable hand waving, absorbing a positive energy regular particle of a virtual pair without absorbing the negative energy particle would break the Heisenberg uncertainty principle.

Re:Quantum Foam

[rasputin465]

As for stellar black holes, the Chandrasaker [sic] Limit is 2.5 solar masses, with a relatively small margin of error.

The value of the Chandrasekhar limit depends on how one performs the calculation, but typically it comes out to around 1.4 solar masses (not 2.5). But actually, this is not so much the interesting question, because the Chandrasekhar limit applies only to white dwarfs, whose mass is supported by electron degeneracy pressure [wikipedia.org]. This is only one type of a much broader concept called fermion degeneracy pressure.

For example, a neutron star is much denser than a white dwarf, and is supported by neutron degeneracy pressure instead of electron degeneracy pressure and hence the Chandrasekhar limit does not apply to neutron stars. The equivalent limit for neutron degenerate matter is called the Tolman-Oppenheimer-Volkoff limit [wikipedia.org]. Like the Chandrasekhar limit, this calculation is very dependent on the behavior of the degenerate matter, but UNlike the Chandrasekhar limit, we know very little about the properties of neutron degenerate matter, and so the uncertainty of the T-O-V limit is quite large; it is usually placed (as you can see in the wikipedia article that I link to) between 1.5 and 3.0 solar masses. And there are even denser objects that have been proposed (though not observed) made of quark degenerate matter, and the limit on the mass of these things is even more uncertain.

So the point is, there is still a good deal of physics that can come from the observation of a 3.8 solar mass black hole, as it can constrain various models of fermion degenerate matter.