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Issue 6.08

The Astrophysics Spectator

September 10, 2009

I'm finally back writing after spending July and August moving across town.  I now know the secret to an easy move to a new house: burn down the old one and everything in it.  This is especially important if you have a thousand books.  With the move behind me, and with my child back in school, I now have the time I need to keep this web site current.

The most powerful explosions in the universe are core-collapse supernovae.  When a massive star exhausts its thermonuclear fuel, its core collapses, triggering an explosion with the release of gravitational potential energy.  This mechanism is thought responsible for all but one type of supernova.

The core-collapse supernova plays a dramatic role in our lives, because only it can create the elements heavier than iron.  Whether gold or lead, a heavy atomic nucleus can only be created in the high temperatures of a supernova shock wave.  The relative scarcity on Earth of these elements compared to the end products of thermonuclear fusion is a direct consequence of the scarcity of massive stars, and therefore of core-collapse supernovae, in our Galaxy.

In this issue, I add the first of several pages on core-collapse supernovae.  This page gives a general description of the mechanisms that generate and transport energy in these explosions.  The next issue will add a page describing the one supernova from which neutrinos have been observed.

Jim Brainerd

Supernovae

Core-Collapse Supernovae.  The most energetic supernovae are powered by gravitational potential energy.  Once a massive star consumes all of its thermonuclear fuel, it is unable to support itself against its own gravity.  The core of such a star collapses to a neutron star.  The birth of a neutron star is heralded by a burst of neutrinos that blows apart the remainder of the star.  We see this expanding debris as a supernova.  (continue)

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