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View Full Version : If we orbited a presupernova



Tom Mazanec
2004-Nov-14, 06:03 PM
Suppose the Earth orbited at the "life distance" from a presupernova (First type1 and the type 2, for this discussion). Ignore the fact that this is scientific nonsense. Would we be able to notice, with 2004 technology, that it was time to say our prayers in the next few days? Maybe neutrinos from a type 2, although those may be enough for radiation poisoning? How about the next several years?

glen chapman
2004-Nov-15, 11:04 PM
Yes we would know. As the star's core cycles through helium carbon al the way to iron, we should get some idea in the spectra and temperatures being detected.

So we would not know the exact moment, but we'd know we are in very deep doo doo

Eroica
2004-Nov-16, 09:46 AM
Yes we would know. As the star's core cycles through helium carbon al the way to iron, we should get some idea in the spectra and temperatures being detected.

So we would not know the exact moment, but we'd know we are in very deep doo doo
Are you sure? Doesn't it take a long time for the photons produced in the core to reach the star's surface (after undergoing repeated absorptions and emissions along the way), whereas the final stages of nuclear fusion take place at increasingly shorter intervals of time? The final stage before implosion - the formation of the iron core - takes hours, I think.

Kullat Nunu
2004-Nov-16, 12:51 PM
Yes we would know. As the star's core cycles through helium carbon al the way to iron, we should get some idea in the spectra and temperatures being detected.

So we would not know the exact moment, but we'd know we are in very deep doo doo
Are you sure? Doesn't it take a long time for the photons produced in the core to reach the star's surface (after undergoing repeated absorptions and emissions along the way), whereas the final stages of nuclear fusion take place at increasingly shorter intervals of time? The final stage before implosion - the formation of the iron core - takes hours, I think.

Final phases of a giant star (from here (http://www-astronomy.mps.ohio-state.edu/~pogge/Ast162/Unit3/supernova.html)):


1) Hydrogen burning: 10 Myr
2) Helium burning: 1 Myr
3) Carbon burning: 1000 years
4) Neon burning: ~10 years
5) Oxygen burning: ~1 year
6) Silicon burning: ~1 day


Unless we can detect the start of neon, oxygen or silicon burning we won't notice anything before the neutrinos born in the core implosion kill us. Although neutrinos are famous in that they don't much interact with ordinary matter, supernova explosion releases such insane amount of neutrinos that they cause the shockwave that rips the star's outer layers apart. So there are more than enough of them to destroy any life on an orbiting planet.

Glom
2004-Nov-16, 01:16 PM
Can neutrinos kill us? Neutrons can, but neutrinos?

Ilya
2004-Nov-16, 02:47 PM
Can neutrinos kill us? Neutrons can, but neutrinos?

Yes, if there are A LOT of them. In those extremely rare instances where neutrino interacts with matter, it hits an atomic nucleus and converts a neutron into a proton and an electron, in effect moving the atom one space up the periodic table - usually into a radioactive isotope. But the word "extremely rare" is relative. I don't have the numbers handy, but from what I read, if you are anywhere in the system going supernova, a significant fraction of oxygen atoms in your body will be converted to fluorine-16, and carbon atoms to nitrogen-12. Both are completely unstable -- F-16 instantly decays into C-12 and He-4, and N-12 into three He-4. So H2O in blood in effect turns into CH2 radicals which join up into C2H4. Which means your first indication of an impeding doom will not be sudden death - it will be slowly increasing pain of bends as you blood vessels are clogged with bubbles of helium and ethylene.

If you escape the explosion AND bends do not kill you, you would still die of radiation sickness because so many other atoms in your body would be converted into raidoactive isotopes. Although technology advanced enough to whisk you away from an exploding star SHOULD be able to deal with radiation poisoning...