How does this happen?

[cirthix]

"Traveling out through space, the light of a supernova is visible across tens of millions of light years. The neutrinos also travel outward -- their initial detection usually proceeds the supernova light by a brief period. "
quoted from http://imagine.gsfc.nasa.gov/docs/science/know_l1/sn_overview.html

 

[unipidity]

Neutrinos are nigh on massless, and hence tend to travel at v ~ c. They are (first) emitted somewhat before the photons, because it is neutrino emission that removes the support pressure in the iron (? mostly) core and causes the collapse that 'is' the supernova.


I also have a question; the 'bounce' that results in so much energy being emitted, and the tearing away of the remnant, is a result of neutron degeneracy, yes? Firstly; what happens to electron degeneracy? Is the 'barrier' just blown right through instantly, wet tissue-like? And secondly, if yes, then for supernova of very large stars that will have a huge core and hence go to a black hole.... why is there a bounce if the force is insufficent to even support the core, never mind the inrushing matter?

 

[cquark]

Originally posted by: cirthix
"Traveling out through space, the light of a supernova is visible across tens of millions of light years. The neutrinos also travel outward -- their initial detection usually proceeds the supernova light by a brief period. "
quoted from http://imagine.gsfc.nasa.gov/docs/science/know_l1/sn_overview.html

Neutrinos are primarily produced by the collapse of the stellar core, while the light from the supernova primarily comes from the following bounce event, so they're produced later than the neutrinos. Neutrinos can also travel through the outer layers of the star as if they're not there, since they only interact through the weak force (billions of them passed through you as you read this message), while photons are readily absorbed and re-emitted by stellar plasma (it takes a photon thousands to tens of thousands of years to make its journey from the core of our Sun to us.)

 

[cquark]

Originally posted by: unipidity
I also have a question; the 'bounce' that results in so much energy being emitted, and the tearing away of the remnant, is a result of neutron degeneracy, yes? Firstly; what happens to electron degeneracy? Is the 'barrier' just blown right through instantly, wet tissue-like? And secondly, if yes, then for supernova of very large stars that will have a huge core and hence go to a black hole.... why is there a bounce if the force is insufficent to even support the core, never mind the inrushing matter?

The iron cores of large, older stars cannot support themselves through fusion since fusing iron doesn't release any energy. They're supported by electron degeneracy. A Type II supernova begins when gravitational attraction exceeds the electron degeneracy pressure.

Once gravitational attraction exceeds electron degeneracy pressure, the stellar core begins to collapse, causing electron capture by protons to form neutrons (and releasing neutrinos and hence energy, hastening the collapse), leading to a core of nuclear density supported by neutron degeneracy.

Your second question is a difficult one. There are two possibilities, and the calculations and simulations done so far can't distinguish between them. The first is that the core collapses into a neutron star, bounces, and then infalling matter from the star's outer layers causes the core to collapse into a black hole. The second scenario is that the core collapses directly into a black hole, without a short-lived intermediary state supported by neutron degeneracy pressure as above. In both scenarios, there's still an outrushing flood of neutrinos into the dense collapsing matter, which would lead to a supernova explosion, with or without bounce. However, direct collapse into a black hole may lead to a hypernova, a hypothetical event that may explain some of the observed gamma ray bursts, as such a collapse would result in two extremely energetic jets emitted from the rotational poles of the new black hole.

 

[cquark]

For a possible future hypernova candidate, check out the very interesting and odd behemoth of a star, Eta Carinae. There's some great pictures from Hubble and a good description at http://www.astrosociety.org/pubs/mercury/9804/eta.html

 

[Gibsons]

Originally posted by: cquark
For a possible future hypernova candidate, check out the very interesting and odd behemoth of a star, Eta Carinae. There's some great pictures from Hubble and a good description at http://www.astrosociety.org/pubs/mercury/9804/eta.html

Whoa, that's cool.