Too Darn Hot

StarDate: April 1, 2010

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Stars are hot, both inside and out. But some stars may be too hot for their own good. Their cores get so hot that the stars blast themselves to bits.


Such a star is born in a region that's rich in hydrogen and helium, which were created in the Big Bang, but that contain almost no other elements. Heavier elements prevent a star from growing to more than about a hundred times the mass of the Sun. So many of these giant stars probably were born soon after the Big Bang, while others are born in galaxies that have seen little change since the Big Bang.

Such a massive star's gravity squeezes the star so tightly that its core temperature climbs into the billions of degrees. That speeds up the nuclear reactions in its core, which "burn" lighter elements -- like hydrogen and helium -- to make heavier ones.

When the hydrogen and helium are gone, the temperature gets so hot that energy produced in the core is converted to matter -- pairs of electrons and their antimatter counterparts, known as positrons.

With some of its energy drained away into matter and antimatter, the star can't sustain itself against its own gravity. It collapses, then rebounds, blasting itself apart as a supernova.

Each of these explosions seeds the universe with heavy elements, which are incorporated into other stars. The later generations can't grow as heavy, so they can't get so hot that they incinerate themselves -- at least not in the same way as their super-heavy predecessors.

Script by Damond Benningfield, Copyright 2010

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