New Type of Star Can Emerge From Inside Black Holes, Say Cosmologists

KentuckyFC writes "Black holes form when a large star runs out of fuel and collapses under its own weight. Since there is no known force that can stop this collapse, astrophysicists have always assumed that it forms a singularity, a region of space that is infinitely dense. Now cosmologists think quantum gravity might prevent this complete collapse after all. They say that the same force that stops an electron spiraling into a nucleus might also cause the collapsing star to 'bounce' at scales of around 10^-14cm. They're calling this new state a 'Planck star' and say its lifetime would match that of the black hole itself as it evaporates. That raises the possibility that the shrinking event horizon would eventually meet the expanding Planck star, which emerges with a sudden blast of gamma rays. That radiation would allow any information trapped in the black hole to escape, solving the infamous information paradox. If they're right, these gamma rays may already have been detected by space-based telescopes meaning that the evidence is already there for any enterprising astronomer to tease apart."

Comments

Its own weight?

[Anonymous Coward]

Black holes form when a large star runs out of fuel and collapses under its own weight

Isn't actually it's own gravity? The weight would increase with the gravity, doesn't it?

Re:Its own weight?

[suutar]

Sort of yes. "...under the force of its own gravitational attraction" would be more precise, I think. Gravity is a force, and weight is the measure of the gravitational force on a particular item. But it's common to think of weight as the force of gravitational attraction itself, and it's shorter to type.

And yes, as it collapses and the distance from particle A to the center of mass of the rest of the star decreases, the force of gravitational attraction (weight) increases.

Re:Its own weight?

[camperdave]

I don't get black hole evaporation. Suppose a proton/anti-proton pair gets created at the event horizon and the proton falls in. Hasn't the mass of the black hole increased by one proton? If the anti-proton falls in, it will meet another proton and annihilate it (assuming conditions within the black hole still allow this), but with no way for the energy to escape, isn't it the same as increasing by the mass of the anti-proton (which is the same as a proton)?

I propose we try the experiment with whomever is supporting this switch to Beta.

Re:Its own weight?

[Anonymous Coward]

I don't get black hole evaporation. Suppose a proton/anti-proton pair gets created at the event horizon and the proton falls in. Hasn't the mass of the black hole increased by one proton? If the anti-proton falls in, it will meet another proton and annihilate it (assuming conditions within the black hole still allow this), but with no way for the energy to escape, isn't it the same as increasing by the mass of the anti-proton (which is the same as a proton)?

That's one interpretation of the effect. The part that you're missing is what those virtual pairs represent. Quantum mechanics allow for the violation of energy conservation laws, as long as the violation doesn't last long enough for it to measured (it doesn't matter if it's measured or not, it matters whether it happens during a time period in which it would be possible to measure it). Virtual particles pop in out of nothing, so suddenly you have extra energy in the universe. Then they annihilate and disappear again before it would be possible to measure their presence. However, in this case, one of them fell into the black hole, the other didn't, so now, from your perspective outside the black hole, you have a brand new particle and therefore extra energy and mass in the universe out of nothing. In order for that to be possible, from your perspective you'd have to witness the other particle as having negative energy. So the particle falling in to the black hole isn't a normal particle, it's a particle made up of negative energy.

It's really hard to visualize that, so luckily there's another interpretation of the same effect that might be easier to swallow. The two virtual particles form inside the event horizon, using energy from inside the event horizon. If they're close enough to the horizon, one of them has a probability of leaving the event horizon through quantum tunneling. I always thought it was easier to visualize this interpretation.

Information paradox?

[gstoddart]

OK, so I understand (vaguely) that this essentially means stuff goes in but doesn't come out.

But if this Planck star bursts forth from a black hole, is any 'information' in a meaningful sense coming back out? Or is the collection of random bits which we defined as 'information' coming back out just a bunch of meaningless noise?

It sounds more like "stuff comes back out, but will have been so mangled by the process that it isn't, strictly speaking, what we'd call 'information'".

I've never been really clear on what is meant by "information" in this context -- it's not like you can figure out that the burst of gamma radiation corresponds to anything specific, it's just a burst of gamma radiation (and whatever else comes out).

Re:Information paradox?

[DeadDecoy]

I think information is used in it's most abstract sense. Any particle or wave signals that that approach the black hole get consumed. I.e. when we look at it, we see nothing because light is absorbed. I'm probably wrong, though, and someone who studies the topic might be more apt at providing an explanation. Personally, I wonder what this means in terms of the second law of thermodynamics. When a black hole consumes energy and releases a Planck star, do either events reduce the entropy of the system?

Re:Beta Sucks!

[Ben4jammin]

I usually try to stay on-topic, but this is a deserved exception.

I logged in, perused some of my old comments just for nostalgia and will be logging out for at least the remainder of the proposed boycott period.

I just wanted to say that it has been awesome being part of the Slashdot community. You guys are awesome. I have lost track of how much I have learned about different topics that I never would have learned were it not for participating in Slashdot discussions.

I hope to see you on the other side...with Beta existing only as a memory of an epic fail.