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Hypernova! - Input Junkie
April 22nd, 2010
07:57 am


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The super-supernova SN2007bi is an example of a "pair-instability" breakdown, and that's like calling an atomic bomb a "plutonium-pressing" device. At sizes of around four megayottagrams (that's thirty-two zeros) giant stars are supported against gravitational collapse by gamma ray pressure. The hotter the core, the higher the energy of these gamma rays - but if they get too energetic, these gamma rays can begin pair production: creating an electron-positron matter-antimatter pair out of pure energy as they pass an atom. Yes, this does mean that the entire stellar core acts as a gigantic particle accelerator.

The antimatter annihilates with its opposite, as antimatter is wont to do, but the problem is that the speed of antimatter explosion - which is pretty damn fast - is still a critical delay in the gamma-pressure holding up the star. The outer layers sag in, compressing the core more, raising the temperature, making more energetic gamma rays even more likely to make antimatter and suddenly the whole star is a runaway nuclear reactor beyond the scale of the imagination. The entire thermonuclear core detonates at once, an atomic warhead that's not just bigger than the Sun - it's bigger than the Sun plus the mass of another ten close by stars.
The entire star explodes. No neutron star, no black hole, nothing left behind but an expanding cloud of newly radioactive material and empty space where once was the most massive item you can actually have without ripping space. The explosion alone triggers alchemy on a suprasolar scale, converting stars' worth of matter into new radioactive elements.

Link from Geek Press.

There are a lot more kinds of nova than I realized.

The only gamma ray burster I can' think of in science fiction is in Egan's Diaspora.

(3 comments | Leave a comment)

[User Picture]
Date:April 22nd, 2010 01:59 pm (UTC)
How does this work?
The entire star explodes. No neutron star, no black hole, nothing left behind but an expanding cloud of newly radioactive material and empty space... What is almost certain is that the core of the star involved in a given hypernova is massive enough to collapse into a black hole (rather than a neutron star). So every GRB detected is also the "birth cry" of a new black hole.

Puzzled. The source article from Nature, BTW, has a comment on it from Eugene Sittampalam, self-styled discoverer of the Theory of Everything. And because I don't have enough to do that lead me to this delightful article on cranks.

Have you heard about LIGO? It's an attempt to detect "gravity waves," based on the prediction that really big phenomena like hypernovae and collisions between supermassive stars ought to send out spacetime distortions. It's a risky business for several reasons (it's so expensive that if the experiment turns out to yield a negative result it's likely to put a significant crimp in astrophysics research budgets for years to come), but one of the risks is that the sort of event they're looking for is quite rare, and they might miss it during building.
[User Picture]
Date:April 22nd, 2010 06:04 pm (UTC)
Any time somebody thinks something's "too big to fail", they should be told about something like this.
[User Picture]
Date:April 22nd, 2010 06:35 pm (UTC)
There's a significant gamma ray burster in Jack McDevitt's The Devil's Eye -- but that's a spoiler...
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