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."

Comments

Re:Probably Something Stupid

[Geoffrey.landis]

I thought that Black Holes had no dimensions, but this one is several miles across. Where have I gone wrong?

A black hole, conventionally, consists of an event horizon surrounding a region of space from which you can't send information to the external world. This region of space is not a point, it has a well-defined circumference. (Because of the non-euclidean nature of general relativity, it doesn't actually have a well-defined radius (since you can't measure across the middle!) but people usually just consider the radius as if it were defined as the circumference divided by 2 pi, and don't worry about the fact that you can't actually measure it.)

At the center of the black hole is, according to general relativity, a point singularity, which indeed has no dimensions.

Re:Size vs Age

[smolloy]

It is true that black holes will evaporate over time, but they will also gain mass from infalling matter.

But!

The temperature of a black hole can be defined by the rate at which Hawking photons are streaming away from it. In the case of a black hole of a few solar masses, this temperature will be in the nano-Kelvin (I think -- don't hurt me if I'm wrong by a few orders of magnitude). Now remember everything in the Universe is sitting in a bath of cold photons from the Big Bang (i.e. the microwave background). These photons have a temperature of ~4 Kelvin.

Therefore, black holes whose Hawking temperature is above the microwave background will be net *gaining* mass.

Which is all a long way of saying, no, this isn't a normal size black hole that has decayed over time. It must have been created at this mass (or smaller).

Re:That's nothing...

[Enoxice]

LHC = Large Hadron Collider: http://en.wikipedia.org/wiki/Large_Hadron_Collider

001 = First black hole created by LHC

Some people are afraid the LHC-001 is going to destroy the Earth.