I thought a supernova's core temperature was absolute zero just before it collapsed, as it has run out of all nuclear and thermal energy, but I haven't been able to confirm this online anywhere and I was wondering if anyone can confirm this for me.

  • $\begingroup$ As far as I know (and I'll let smarter people than me answer this, so I'll just comment), but not even close. The fusion process slows down significantly and that makes the collapse possible, but there's too much heat present for it to cool down much as the fusion slows down. It's still inside of star temperature - many millions of degrees, and the temperature likely shoots up might higher than that, probably into the billions as the core collapses. $\endgroup$
    – userLTK
    Oct 21, 2015 at 11:12
  • $\begingroup$ You can't just kill the heat by switching off fusion, you have convection and radiative processes which will keep the temperature from being anywhere near absolute zero. We also have the fundamental laws of thermodynamics to contend with. Absolute zero is not possible. $\endgroup$ Oct 21, 2015 at 18:32

1 Answer 1


No, absolutely not. The core of a core-collapse supernova is one of the hottest places in the present-day universe. The temperature as the star runs out of nuclear fuel in its core is around 6-10 billion Kelvin. As it collapses, the core gets even hotter, perhaps as high as 100 billion Kelvin for a few seconds, before neutrino cooling starts to become effective.

We know that the temperatures are getting as high as this because at least two neutrino instruments on Earth detected roughly "thermal neutrinos" with energies of $\sim 10$ MeV coinciding with SN1987A in the Large Magellanic Cloud (see for instance Mirizzi et al. 2015).


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