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That was pretty much my take. - Edit 1

Before modification by Joel at 13/08/2013 03:15:35 AM


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On the other hand, there's no real reason to believe it will happen in the next couple of hundred years or so, is there?

Not really, no. The article reads like a bit of a tease (but then, Daily Mail ) despite, or perhaps because I know that, contrary to the portrayal in Star Trek episodes, supernovæ provide practially no advance warning. There is the neutrino burst, of course, but that is from the explosion, so like the old "FLASH—duck and cover" drills: By the time you see it, it is already too late. Stellar collapses are detectable, but significant periodic expansion/contraction is common in very massive stars, so that is an unreliable predictor. Betelgeuse is a good example: As the article notes, it contracted a lot a few years ago, prompting scientific speculation it was about to go (and apocalyptic speculation the Mayans predicted it ) but now it is back to "normal" (by variable star standards.)

Flip side, EXPANSION of the most massive stars sometimes expels enough matter to create "supernova impostors," exposed as such once enough dust clears to reveal the star still cooking away behind it. That may be the most practical early warning system, because supernova impostors sometimes precede the Real McCoy by VERY brief spans; in the case of SN 2006jc, by just two years. I have never heard of Betelgeuse doing anything that extreme, but about 150 years ago another imminent "hypernova" candidate did: Eta Carinæ.

Although about fifteen times farther away than Betelgeuse, Eta Carinæ (or its binary systems primary) is among the most massive stars we have found, leading one Berkely astronomer to predict its hypernova will be bright enough on Earth to read a book by at night. The Wikipedia folks claim it is no threat to anyone but astronauts, because its pole is not currently facing us. If it were, the gamma ray burst would instantly exterminate all life on the planet—from a distance of 8000 light years. A nice little reminder of just how precarious terrestrial life is.

Unfortunately for you (and, at present, me) Eta Carinæ is never visible beyond 30°N; even in TX, even at its zenith, it is near the horizon.

In general, it looks our best chance of seeing a nice supernova coming is to keep track of impostors. Not only do they often portend actual supernovæ, they tend to occur in the most massive stars, whose radiation is so high gravity is only just barely holding them together already, so they tend to produce the brightest longest lasting super/hypernovæ. Then the question is just whether we are close enough to get a good view.

SN 2006gy, Eta Carinæ and potential super/hypernovæ harbingers

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