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

Size vs Age

[__aapbzv4610]

While it may be possible that this black hole was formed from a relatively small (to form a black hole) star, couldn't it also be the case that it just a really old black hole? Hawkings told of how black holes can 'evaporate' over time with lack of surrounding matter, perhaps that could be the case here.

Re:Size vs Age

[tardyon]

Perhaps you can answer a question for me. If I understand the concept correctly (and stop me where I go wrong), the event horizon can be defined as the point where any light that were to be ejected (I know, I know not possible) from the singularity perpendicular to the tangent (straight "up") would stop and return. This is the Newtonian description of a black hole. The relativistic description is considerably more complicated. First of all, you must always start any relativistic description by stating your reference frame - i.e. who is making the observations? The Schwarzschild metric (which is the standard non-rotating black hole) takes the observer to be someone infinitely far away and not moving relative to the black hole. According to that observer, there is a singularity at the event horizon. Anything inside the horizon is effectively in a different universe. Anything outside of it takes an infinite amount of time to fall all the way to the horizon. As stuff gets closer to the horizon, its time rate slows down and the radiation it emits gets red-shifted. There's no point in saying what the distance from the horizon to the singularity is in this frame of reference because the horizon IS the singularity. Equally, the space inside had no volume; in fact, the "space" inside isn't even space-like, whatever that means.

Given the relativistic time stretching effects that this implies, as I understand it, anybody falling in would experience "the end of the universe" as time around him speeds up infinitely. Now we're in a new frame of reference, that of the person falling in. In this frame of reference, the event horizon is nothing special. In fact, for the huge black holes theoretically at the centers of galaxies, someone falling through the event horizon doesn't notice much at all, even the tidal forces are fairly tame. As far as they are concerned, time keeps marching on happily and they keep falling, and their only discomfort is the increasing tidal forces they experience. Also, the rest of the universe slows down. They categorically do not see the end of the universe. They also never see the singularity. If they fall feet first, they don't even feel their feet hit the singularity as their brain hits the singularity before light can travel from the space-time event of "foot hits singularity" to the brain. I can do the proof, but I'm not entirely sure I understand this concept. :) This is irrelevant however since tidal forces will rip them up before they hit the singularity.

My question is, assuming that I am not simply mistaken about the relativistic effects of the event horizon, is; what happens to that item falling into the black hole when the black hole evaporates? That's a very good question. In principle, the answer is that anything that falls into the black hole hits the singularity and gets utterly destroyed. There's a lot of concern about what really happens to the "information" about what went in, but it's probably irrelevant to your question. Whatever comes out, it's not what you or I would consider to be recognizable based on what went in. If you fall in, you won't reappear after the black hole evaporates. Instead, a slew of random (or possibly not so random) elementary particles with the same total mass that you had will be emitted over the course of trillions of years. It's a brilliant paper shredder.

untrue statement

[ILuvRamen]

They can't figure out the "critical threshold" because there isn't one. It all depends on too many variables to set a universal limit (hehehe get it...universal :-P) It depends on how much nuclear activity there is still going on when it start collapsing and what the amount of heavier atoms is and the amount of other things orbiting the star and any other forces affecting the star at that time and how fast it's moving and spinning. Mass is a smaller part of the calculation than they're making it sound like. If they're going to factor everything in just to find some minimum mass, well duh, two particles and a hell of a lot of force. Haven't they suggested that in that big particle accelerator aka donut of doom. So yeah, a critical mass threshold doesn't exist.

Re:The Earth in danger from microscopic black hole

[Anonymous Coward]

ok, I am ripping most of the info from here: http://www.physicsforums.com/showthread.php?t=122375&page=6

        "If they were able to make a small blackhole, and it got "loose" and fell to the center of the Earth, the pressures at the Earths core would force material into it so fast that even a very small one would gobble us up very fast. I am not sure what the exact pressure is at the Earths core but it could force material through even a very small "hole" very quickly. I do agree that once it gobbled up the Earth, it would just continue to orbit the Sun, and the Moon would still orbit the blackhole as if it were the Earth..."

No, you should read this thread.

First of all, a black hole that falls to the center of the earth, wouldn't stop there, but would continue falling up on the other side, just to plunge in again, and on and on, because there's no "friction" on the black hole.

Second, there have been posted in this thread a lot of calculations of the speed at which it would gobble up matter.
Don't forget that the black hole we're talking about here IS MUCH MUCH SMALLER THAN A PROTON. As such, pressures on *atomic* level (such as in the center of the earth) matter little: the black hole travels most of the time in the empty space between nucleae.
A way to calculate the probability of hitting a nucleus (and somehow imagining that it would gobble up the entire nucleus, which is MUCH MUCH bigger than the black hole itself - which is a worst-case scenario) is done by calculating the "cross section" of the black hole and its probability to cross a nucleus on its voyages through the earth. We know its speed (just falling), and knowing the cross section and the density of nucleae, we can estimate how many nucleae it could eat per unit of time.

For a classical black hole, the calculation is done in the link provided by Pervect in this post:
http://www.physicsforums.com/showpos...4&postcount=12

for a MUCH LARGER black hole, about the size of a proton, weighting a billion tons (figure that! A black hole *the size of a proton* weights a billion tonnes ; we're talking here about black holes that weight 10 TeV or 10^(-24) kg - go figure how small it is !)

For more exotic calculations which are more severe, orion made some, and arrived at a time to eat the earth ~ 10^46 years.

All this in the following rather un-natural hypotheses:
- no Hawking radiation (which would make the black hole evaporate almost immediately)
- production of black hole EXACTLY IN THE CENTER OF GRAVITY of the collision (no remnant particles)
- very high production rate, producing billions of black holes per second.

I am not a physicist, but from what little physics I have had, and from reading threw the thread/flamewar, I dont think we have to worry about the LHC

Re:Probably Something Stupid

[dmartin]

Actually, the Schwarzchild solution does have a well-defined radius. In fact, the problem is that it has many well-defined radii, depending on what you mean by the term (as you point out, this comes about because of the non-Euclidean nature of the geometry). The commonly quoted "Schwarzschild radius" r = 2GM/c^2 is obtained by taking the area of the horizon and figuring out which "r" you would have to plug into A = 4 pi r^2 [true for a flat space sphere] to get the right result. Taking the circumference and dividing by 2 pi would achieve the same result. However, it is quite possible to figure out the proper distance between the horizon and the singularity by measuring the distance an infalling observer would travel. This distance is finite.

A problem can occur if you try and use constant time slices, using the "natural" time coordinate as defined by an observer far from the black hole. This gives silly results, but that is only because of badly behaved coordinates.

Re:Probably Something Stupid

[Geoffrey.landis]

Actually, the Schwarzchild solution does have a well-defined radius.

No, actually it doesn't. What is usually called the Schwartzschild "radius" is not actually a radius by the definition of the word, "distance to the center".

In fact, the problem is that it has many well-defined radii, depending on what you mean by the term (as you point out, this comes about because of the non-Euclidean nature of the geometry). The commonly quoted "Schwarzschild radius" r = 2GM/c^2 is obtained by taking the area of the horizon and figuring out which "r" you would have to plug into A = 4 pi r^2 [true for a flat space sphere] to get the right result.

Exactly. You can calculate the area (which is well defined) and divide it by 4 pi, and you are free to call that the radius if you like. Or, equivalently, divide the circumference by two pi. But you can't measure the distance to the center.

Taking the circumference and dividing by 2 pi would achieve the same result. However, it is quite possible to figure out the proper distance between the horizon and the singularity by measuring the distance an infalling observer would travel. This distance is finite.

Finite... and timelike. It would be a little like trying to define the radius of a circle if you're standing on the circumference, and the center is next Tuesday at noon.

A problem can occur if you try and use constant time slices, using the "natural" time coordinate as defined by an observer far from the black hole. This gives silly results, but that is only because of badly behaved coordinates.

Within the event horizon, any choice of coordinates is rather badly behaved, because there is no well-behaved stationary coordinate system.

Re:Probably Something Stupid

[afaik_ianal]

Is there a theoretical way to revert a singularity? In theory, they radiate themselves out of existence over time through Hawking Radiation. They constantly release energy, which reduces their mass. If they lose more mass than they swallow, then their event horizon will shrink. Eventually, there'll be no mass left, and no black hole.

Rotating black holes [Re:Probably Something S...]

[Geoffrey.landis]

Actually, that's only true of a non-rotating (or Kerr) singularity. Yeah, I thought about mentioning that, and decided what I was writing was getting a bit complicated already

All natural black holes will be rotating (the black hole maintains the rotational momentum of the pre-collapse mass).

Well, maybe. Actually, rotating black holes radiate away angular momentum, and they also preferentially eat material that reduces their angular momentum, so it's an open question as to whether real black holes will be rotating. Probably, because the accretion disk is likely to be rotating, and it swallows up the accretion disk and gains the momentum from it, but I'm not sure you can necessarily say that all natural black holes will rotate.

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.

Actually, the Einstein-Rosen bridge comes from the maximum analytical extension of the Flamm embedding, way predating the Kerr solution. (It's a very trivial embedding, z = sqrt(r). The extension is z = plus or minus sqrt(r).) Turns out that the extended Flamm embedding is misleading, and a Schwartzschild black hole isn't a wormhole after all. But that wasn't obvious.