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Black Hole Birth Detected this Morning
An anonymous reader writes "SPACE.com is reporting on the first optical afterglow ever detected from a short-duration (milliseconds) Gamma-Ray Burst. The GRB signals the birth of a black hole resulting from a merger between two neutron stars. Theory had predicted the whole thing, which was all spotted this morning by NASA's Swift satellite and ground-based observatories, thanks to an automated email system that notifies astronomers worldwide."
Wasn't there another slashdot article a few weeks ago about how blackholes don't exist? I think it was talking about this report.
Found it. Donald Coyne of UCSC gave a talk on the Ultimate Fate of Small Black Holes. Be sure to check the Milagro link on his facutly page.
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There are different types and different source of gamma ray bursts. Hypernovas, neutron star mergers, black hole mergers, etc.
From what I've read, you have a better chance of detecting a black hole by looking for the effects of its gravitational field on light that passes nearby. It should warp the apparent positions of stars.
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You're probably joking, but you got modded informative so:
From your link "according to a physicist"... There is a general consensus that black holes with singularities exist, but the universe doesn't give a damn about our consensual opinion - the Earth would be flat otherwise.
This is how science works, people come up with testable ideas which are proven right or wrong. No-one is arguing that super-dense, intrinsically dark objects don't exist, we have plenty of evidence that they do. Infinitely dense singularities, well, maybe not - if they exist as we predict they're inside an event horizon and therefore unobservable so actually directly verifying their existance is always going to be impossible... all we can do is come up with odd ideas like dark energy stars which might bounce matter out and see if we can observe that happening.
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Black holes are detectable. The accretion disk about the even horizon emits a lot of gamma rays, because matter falling into the hole are accelerated like crazy. Once matter has reach the even horizon of course, nothing escapes.
Think of it as a last cry of atoms being swallowed.
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Gamma Ray Burst 2005 05 09 b
I would guess that it was the second gamma ray burst (candidate?) detected (since 1200 GMT?). Lot of guessing on my part though.
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There are long and short GRB events. This was the first time an optical afterglow was detected for a short event. The theory was that long and short GRBs were caused by similar events, and we should see an afterglow for both - which, of course, is the evidence that was found.
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Real image: (Note it is a negative - black means lots of light. The big thing in the middle is a galaxy, and the error box is pointing to somewhere on its outer edge.)0 9.jpg
http://www.srl.caltech.edu/~cenko/grb050509b/0505
What they detected was a gamma ray burst and an afterglow. Everything else is speculation; they are basically saying "if all our theories are correct, then the explanation that this is two neutron stars merging into a black hole is the most plausible explanation". The observation does not provide any additional evidence that black holes exist.
It's the other way around. Astrophysicists thing that the long and short bursts are generated by different processes.
The current leading theories are that the long bursts are caused by enormous stars going supernova. However, instead of forming a neutron star in the middle, they form black holes. The resulting accretion disk in the star's center accelerates a jet to near the speed of light, and if we look down along the axis we see a burst of gamma rays as it breaks out of the star and then hits the interstellar medium.
The short bursts are thought to be due to two neutron stars colliding. The result is also a black hole + accretion disk, however the timescales involved are much smaller because the jet doesn't have to break out of a dense stellar core in order to be seen.
There are other theories... but they are less accepted. One of them is that some neutron stars are metastable - and could spontaneously `tunnel` into something with a denser equation of state i.e. a quark star. This would release a huge amount of energy, and could possibly explain some GRBs. Another option is that a neutron star could be held up by centrifugal force, and if it spins down enough it would collapse into a black hole, with a resulting accretion disk + jet.
They're both caused primarily by black hole formation, though. Other hypotheses about GRBs have been quite diverse, as you point out. It's a good point that GRBs are probably caused by a variety of events. The X-Ray and optical afterglow is the signature of black hole formation (by one means or another), which had been predicted for the short bursts and confirmed for some of the long bursts.
As I understand it, the biggest GRB we've seen in our galaxy was not thought to be black hole formation, however, but a collapse of magnetic energy around a neutron star. I don't understand that one myself.
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The event you mention that happened in our galaxy was not a GRB. It was a soft gamma ray repeater, which is completely different. If you look at the light curves, a GRB tends to be 'spikey' or a smooth hump, or something in between. Whereas a soft gamma ray repeater has an oscillatory spectrum - there is a spike followed by lots of reverberation. The other big difference between the two classes of events is that soft gamma ray repeaters repeat; Every ten years or so a given object will have an event. GRB's are totally different - they go off, and then are never heard from again.
Astrophysicists think that soft gamma ray repeaters are due to the decay of extremely strong magnetic fields (strong enough to almost cause vacuum breakdown) in a class of neutron stars called `magnetars`. The reverberation seen matches the period of a pulsar in the error box in at least one case. However, just as we don't know exactly how pulsars pulse, the exact emission mechanism for soft GR repeaters is poorly understood.
Extremely experienced scientists dumb down their talks all the time for lay people. When I give a talk to my colleagues, I use entirely different language and skip over very basic stuff that I definitely do go over when I talk to the general public.
From an event such as this 2.2 billion light years away, the gravity waves would be negligibly small. The LIGO detector will not be sensitive enough to detect merging neutron stars farther away than the local galaxy cluster (10 million light years in diameter).