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The Question
(Submitted November 07, 1996)
Is it possible that the Sun could just burn out?
What manages to keep the Sun so hot all of the time?
The Answer
The Sun is basically a thermonuclear bomb with a built-in thermostat. Just
as in a hydrogen bomb, hydrogen atoms are fusing together to make helium atoms
and this nuclear reaction produces heat (along with the light that we see).
If the reactions go on too fast, the Sun expands slightly (just like a balloon
expands when you heat up the air in it). This slows down the reactions and
then the Sun cools and contracts. If it contracts too much, the nuclear
reactions speed up, and then the Sun heats up and expands again. So the Sun
stays at the same temperature, burning its nuclear fuel at a steady rate. At
the rate it is going, we have about 4 billion years left until the Sun burns
out
Andy Ptak and the Ask an Astrophysicist team
Questions on this topic are no longer responded to by the "Ask an Astrophysicist" service. See http://imagine.gsfc.nasa.gov/docs/ask_astro/ask_an_astronomer.html
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