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A supernova remnant is the structure resulting from the explosion of a giant star. The supernova remnant is surrounded by an expanding shock wave that is formed from material ejected by the explosion and interstellar material swept away during the process.

When this material collides with the circumstellar or interstellar gas, it forms a shock wave that can heat the gas at high temperatures up to 10 million K, forming a plasma.

The first question is: exactly what is the material ejected by the supernova?

The other issue is: if we consider for a moment the idea that a "human" might be witnessing the exact moment of the explosion of a supernova, the "superhuman" would hear the explosion? That is, does the explosion produce some kind of sound?

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Could you go and edit your question a bit? Some key words appear to be missing that could cause confusion. –  Larian LeQuella Sep 10 '11 at 16:19
    
Crossed-posted from Physics.SE. –  Qmechanic Aug 14 '12 at 12:53
    
Part of this question duplicated: physics.stackexchange.com/questions/35156/… –  Chris White Dec 27 '12 at 10:56
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Supernovae explosions are more violent than novae explosion. In a typical novae explosion star sheds just the outermost layer of it's mass.

Well, supernovae are the explosive events caused in case of high mass stars, after the iron core is formed at the centre. As iron is most stable element, no further fusion takes place and stars central engine stops for final time, this disturbs the equilibrium, and gravity starts dominating. The star collapses where "photodisintegration" and "neutronisation" takes place. At this point of time the density reaches of the order of $10^{17}$ $kg/m^3$, the collapse is eventually halted by neutron degeneracy pressure, and star explodes, where it's huge matter is thrown in space. Hence, materials ejected by supernovae are many higher elements formed during the different fusion cycles. It is also believed that during this explosive event elements higher that the iron are formed.

Well, coming to the second question, obviously sound is produced. You can hear it if you are connected with star by interstellar matter. I mean to say, if there is vacuum between you and star (i.e you are extremely far) then you will not hear the sound, unless until the shock waves reaches you.

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