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When a supernova explodes, does it eject chunks of solid material in the form of asteroids (of any size) or is it all just dust and gas that later clumps together into bigger solid objects? Or is all the material completely atomized such that the largest thing ejected might be an individual cesium atom?

Another way of asking the same thing: How large (or small) might the largest solid object ejected from a supernova be?

Wyck
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  • A supernova involves the violent explosion of a star. All of the debris will be ionized gas, i.e. plasma. No solid chunks at all. – Jim421616 Mar 24 '24 at 19:15

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At the time of the supernova, the material ejected is not solid or gas or even atomized, it is exclusively ionized nuclei and free electrons, protons, and highly energetic photons and neutrinos. It is the latter which would rip any atom as soon as it would form. Slowly over the next 10,000 years or so the expanding bubble of material cools and seemlessly blends into the interstellar medium, some percentage of the plasma recombining into a gas and an even smaller percentage molecularizing, which is what gives supernova nebula their colorful appearance. However the interstellar medium is always to some extent ionized, so it can be said that much of the remnant of a supernova remains as a plasma even long after it has occurred.

Eventually the shock wave from the supernova can ripple through the ISM and cause a molecular cloud lightyears away to become unstable and begin to collapse under gravity, which would then begin to clump that gas and dust into stars and planets and asteroids, but otherwise the material from the supernova just becomes and remains a part of the interstellar medium forever.

Anthony Khodanian
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  • The defining characteristic of a type II supernova is hydrogen absorption lines due to atomic hydrogen. – ProfRob Mar 26 '24 at 20:33
  • @ProfRob: is it atomic hydrogen at the point the material is ejected from the shattered star, or is does it get ejected as a plasma and recombine further out (and is it the cooler, reassembled atoms that our instruments pick up)? – Greg Burghardt Mar 26 '24 at 21:00
  • @ProfRob I'll admit plasma physics was not my area of study, but iirc the emission and absorption lines of atomic hydrogen are present even in a pure hydrogen plasma, and is how we can characterize its temperature and electron density. There will always be some rate of recombination and reionization in any plasma, and as the supernova emmisions cool more and more of the hydrogen will remain recombined. I do know that by the time the supernova is able to be characterized into type I or II, the ejecta is days old and has cooled to the point where yes, we should expect much of it to now be a gas. – Anthony Khodanian Mar 26 '24 at 21:39