Outrageous new means of megastar demise spotted Most big old stars at the end of their lives tend to go out in a fairly mundane way - either exploding with incredible violence as supernovae, or collapsing into ultradense universe-warping unfeasiblo-gunge as a black hole. But now astronomers say they have seen evidence of a long-hypothesised third path for a large star; that …
I trust our region of space (indeed the whole Galaxy) is sufficiently filthy with heavy elements that this sort of thing is unlikely to blow us all to Kingdom Come.
Still, plenty of other things to worry about. A well-aimed GRB occurring somewhere in the Milky Way might yet scour the Earth clean of all life.
http://dx.doi.org/10.1017/S1473550404001910
(As an aside, does anyone else find it interesting that "Milky Way Galaxy" is a rhetorical tautology? No? Just me, then.)
the mini big bang... the galaxy destroyer supernova... Hypernova
This summer in theaters, watch as <insert action hero name> played by <insert action movie actor name> tries against all odds to save the galaxy from impossible odds...
Mines the one with the dark matter in the pocket
was very curious about the antimatter claims here as I didn't know how it could possibly be produced nor how it could accumulate to cause a significant explosion so, as ever, wiki to the rescue. It seems that antimatter can be produced thusly <http://en.wikipedia.org/wiki/Pair_production>, this article leading on to the actual suspected mechanism in <http://en.wikipedia.org/wiki/Pair-instability_supernova>, which says something fractionally more prosaic may have happened:
" For very high mass stars, with mass at least 130 and up to perhaps roughly 250 solar masses, a true pair-instability supernova can occur. In these stars, the first time that conditions support pair creation instability, the situation runs out of control. The collapse [caused by the redirection of energy production from photons, pressure from which keeps the star 'inflated', into the production of antiparticles, which presumably somehow don't] proceeds to efficiently compress the star's core; the overpressure is sufficient to allow runaway nuclear fusion to burn it in a few seconds, creating a thermonuclear explosion. With more thermal energy released than the stars' gravitational binding energy, it is completely disrupted; no black hole or other remnant is left behind."
So by my reading it's not directly antimatter driven and I really must must must stop getting distracted by Lewis' articles and do some bloody work instead.
@Chris W: about the size of the turtle at the bottom. P'raps.
Contrary to the article, pair-instability supernovae aren't "antimatter-driven". Pair production does occur, but it is not the source of the energy in these events.
Once gamma rays inside the star reach sufficient energy that pair production begins to take place*, the gamma rays don't go as far and the photon pressure they would normally supply to the upper layers of the star decreases, thus causing further collapse, higher temperature, higher-energy gamma rays, and a runaway reaction that causes the star to generate enough heat to overpower the star's ability to hold itself together under gravity. The electron-positron pairs form from gamma rays, and end up as gamma rays when they annihilate with something--the process does not produce energy that wasn't already there in the form of gamma rays. Pair production is merely the mechanism of instability--hence the name "pair-instability supernova"--as it interferes with the propagation of the gamma rays whose photon pressure is vital to the survival of the star.
*The energy of the gamma ray (E = hf) must exceed twice the rest mass of an electron in order to produce an electron-positron pair. I should probably add, though it is not a major hang-up inside a star, that pair production only takes place in he presence of something like an atomic nucleus; otherwise, the process would violate conservation of momentum as, without the nucleus being there to receive the momentum of the original photon, the electron-positron pair (these particles having mass) must invariably have less momentum than the original gamma ray. Consider the case of a gamma ray whose energy is exactly twice the rest energy of an electron (that is, E = hf = (m_e)*c^2). In this case, the electron-positron pair would have no kinetic energy and thus no momentum whatsoever, even though the gamma ray that produced them had a momentum of p=hf/c.
Will be the death of us all!
Secondly, at one time wasn't it somewhat discouraged (if not openly mocked) if someone quoted wiki?
@yossarianuk: It's only a matter of time now, but don't forget about additional taxes, fees, licenses and tariffs to save the planet from imminent threats of more warming/cooling, partial or total obliteration. Oh yeah, and think of the children...
Suddenly, I care even less about global warming than I did before (which wasn't much).
Being a lazy sod, I'm far more interested in the implied use of matter/antimatter explosions for sock removal.
If a megastar of this type exploding in our galaxy would knock everyone's socks off, how much antimatter do you think I'd need to easily and reliably remove one pair of socks at a range of somewhere around three meters?
i had clicked under the pretense that the LHC had found an entertaining way to dispose of celebutards... don't get me wrong, it is interesting reading non-the-less, but with a dissapointing absence of death, dismemberment and such like...
Paris, for the lack of death of.
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