Well. Seeing as how there seems to be such a black hole enthusiastic crowd in the theater tonight, I thought this bit of news might find some eager ears or eyes. It would appear that the mystery of what causes the gamma ray bursts of 0.3 seconds or less have now been pinned down to either two neutron stars merging to form a black hole or a neutron star merging with a black hole. All that I have access to is a short synopis printed in Science. The original papers are in Nature ("This weeks" issue of Nature is all it said...) and I don't have access so perhaps some of the enthusiasts can dig up the particulars as the Science article is rather vague: "Now, follow-up observations of the afterglows of two short bursts on 9 May and 9 July, detected by the Swift and HETE-II satellites, respectively, have settled the issue. The bursts, which occurred in relatively nearby galaxies, showed no hint of an underlying stellar explosion. Given their distances, they appear to have less than 1/100th the power of their longlasting cousins. These observations agree perfectly with the merger model, in which two orbiting neutron stars—themselves compact remains of exploded giant stars—slowly spiral toward each other and coalesce into a black hole, releasing huge amounts of energy Unpublished results from three more short gamma ray bursts support the conclusions, says Jochen Greiner of the Max Planck Institute for Extraterrestrial Physics in Garching, Germany. “The general feeling in the gamma ray burst community is that the issue has been settled,” he says. “I am not aware of any remaining viable alternative explanations.” " The longer bursts were already known to be caused by supermassive stars going hypernova while their cores implode into black holes. Hopefully one of these bad boys will never occur close to home and pointing right at us.... Hmm. Question. Would these shorter bursts be as deadly as the larger ones would be? Also, I seem to recall these being directional bursts, yes? So they'd have to be pointing directly at us for us to detect them? (And for them to kill us all if one went off in our general vicinity?)
This NASA press release is longer. http://www.nasa.gov/mission_pages/swift/bursts/short_burst_oct5.html
Yes, the jets are two beams rushing in opposite directions. We would be unlucky if two neutron stars or a neutron star and a black hole merging in our vicinity decided to shoot a jet in our direction, but the chances are not zero
