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gordo
2009-Aug-17, 03:21 PM
Pleased to be here. Looks like there's a lot of stuff to do and learn!

I've been wondering what the time length is when a star explodes-at least from the initial condensed orb state to the beginning of the expanded gas/dust state. Would it be in human terms just a flash or would it be days or a year?

robross
2009-Aug-19, 01:16 AM
Pleased to be here. Looks like there's a lot of stuff to do and learn!

I've been wondering what the time length is when a star explodes-at least from the initial condensed orb state to the beginning of the expanded gas/dust state. Would it be in human terms just a flash or would it be days or a year?

I'm not exactly sure what you were trying to describe with the orb/dust state.

But there are many different kinds of nova/supernova/hypernova explosions and they all act a bit differently. However, in general, once a star loses the battle between gravity and the pressure from nuclear fusion, the explosion is virtually instantaneous by our standards. The brightest part of the explosion only lasts briefly, from a few days to a week or so, then slowly reduces in strength over a period of weeks and months.

Rob

trinitree88
2009-Aug-19, 08:04 PM
Gordo. The only data we have from SN1987a, indicates that the neutrinos released had a periodicity, and were in a series of closely spaced bursts. That says that the expanding core and it's peripheral envelope oscillated a bit, kind of like a bouncing superball, with the neutrinos escaping with successive bounces of density.
Although we did not see a gamma ray burst, we have since learned that they are highly directional in collimated jets, by a factor of ~ 10,000, and the three dimensional scenario proposed initially by Peter Nissenson, et al, and later corroborated by J. Middleditch was that the explosion jettisoned two jets of material from both poles at nearly c before continuing it's overall axisymmetric expansion. (there was likely a GRB, which may later show up as a light echo) Early disputes of this model were incorrect, despite the general misgivings of the scientific community over the speckle interferometric results by Nissenson, and the dubbing of the ejecta on the cover of the magazine Science News....Son of Supernova. pete

see:http://en.wikipedia.org/wiki/SN_1987A

speckle image following supernova 1987a see:http://www.iop.org/EJ/article/1538-4357/518/1/L29/fg1.jpg?request-id=b383a790-8df3-4e17-85c0-72f56a24bfba