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

[Ecuador]

While black holes is not my area, I can tell you that when someone talks about the size of the black hole, they refer to the event horizon, since you can't really measure anything going on inside it.
The mass of the black hole is the most defining characteristic.

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:As someone who skimmed A Brief History of Time

[BoChen456]

I believe they are referring to the diameter of the event horizon

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.

Re:Probably Something Stupid

[The Only Druid]

Actually, that's only true of a non-rotating (or Kerr) singularity. All natural black holes will be rotating (the black hole maintains the rotational momentum of the pre-collapse mass). In a rotating black hole, the singularity is actually a ring (or torus). Inside that ring/torus, there is a tear in space.

It was this tear that lead, if I recall, to the original conjectures of a white hole, and the Einstein-Rosen bridge.

Quantum Foam

[jd]

There are going to be a near-infinite number of quantum-scale black holes and wormholes in whatever volume of space you care to imagine. They evaporate almost instantly. As for stellar black holes, the Chandrasaker Limit is 2.5 solar masses, with a relatively small margin of error. Absolutely nothing of interest will be learned until we're within 2.75 solar masses, because then we can define sensible confidence limits on what the value actually is.