"Burning Walls" May Stop Black Hole Formation 100
KentuckyFC writes "Black holes are thought to form when a star greater than 4 times the mass of the Sun explodes in a supernova and then collapses. The force of this collapse is so great that no known force can stop it. In less massive stars, the collapse cannot overcome so-called neutron degeneracy, the force that stops neutrons from being squashed together. Now a Russian physicist says another effect may be involved. He points out that quantum chromodynamics predicts that when neutrons are squashed together, matter undergoes a phase transition into "subhadronic" matter. This is very different from ordinary matter. In subhadronic form, space is essentially empty. So the phase change creates a sudden reduction in pressure, forcing any ordinary matter in the star to implode into this new vacuum. The result is a massive increase in temperature of this matter that creates a "burning wall" within the supernova. And it is this burning wall that stops the formation of a black hole, not just the degeneracy pressure of neutrons. This should lead to much greater energies inside a supernova than had been thought possible until now. And that's important because it could explain the formation of high energy gamma ray bursts that have long puzzled astrophysicists."
QCD Phases (Score:4, Informative)
Supernovae (Score:2, Informative)
"Black holes are thought to form when a star greater than 4 times the mass of the Sun explodes in a supernova and then collapses. "
If a star is greater than _8_ solar masses you get a supernova.
Re:I love this kind of story (Score:4, Informative)
Facts... like unexplained Gamma Ray Bursts?
I mean, this is more of synthesis of existing observations rather than *new* observations, but it's still science.
It's taking unexplained observations and incorporating those observations into better theories that fit the data. I'm not an astrophysicist, and this still seems like it's just an hypothesis, but I guess I don't see where the problem is.
Re:Spoiler! (Score:4, Informative)
Reading comprehension FAIL: exactly the opposite is true. Our star will NOT supernova and form a black hole because our sun is EXACTLY one solar mass (being the star that scale is based on) which is less than eight solar masses.
Re:Scientific method to the rescue (Score:2, Informative)
observational tests? (Score:5, Informative)
There are a lot of very difficult theoretical problems involved in trying to describe the structure of neutron stars. The classic picture of a star made of nothing but neutrons is probably not quite right, and is possibly qualitatively wrong in important ways. There's supposed to be an upper limit on the mass of a neutron star, and the theoretical uncertainties get greater as you get closer to this mass limit. E.g., it's possible that you get quark stars. We just don't know, because we don't know the behavior of the strong and weak nuclear forces with sufficient precision to be able to extrapolate to these extreme conditions.
Given all that uncertainty, which has existed for many decades, it's not at all surprising to me that there's a corresponding uncertainty about the conditions under which a neutron star is or isn't unstable with respect to collapse into a black hole. The paper [arxiv.org], which is linked to from the end of the Technology Review article, is pretty heavy going. My field is nuclear physics, not relativistic astrophysics, and I had a hard time understanding it. The author's English is also pretty hard to understand, so it's hard to tell exactly what he's saying his conclusions are. But if you look at the end, he seems to be suggesting that black holes actually do not form.
I wonder to what extent existing observations constrain this idea. For instance, we know that the Sagittarius A* object at the center of our galaxy has a mass of at least 3.7 million solar masses and a radius of less than 6.25 light-hours. It would be interesting to know what he proposes this object is, if he says it's not a black hole.
Re:Spoiler! (Score:3, Informative)
Sorry, but by the time our sun has passed through it's red giant phase it will be considerably LESS than one solar mass.
(I've always wondered at what point in a stars life they count it's weight for that phrase. Possibly they're uncertain enough about the exact value that it doesn't matter, but I think the sun is expected to shed something approximating 1/4 of it's mass during the red giant phase, so that's a lot of uncertainty.
OTOH, I'm definitely NOT a astrophysicist, and I might be off in how much mass the sun is expected to shed by quite a large amount. All I really know is that it's not an insignificant amount.)