MadSci Network: Astronomy

Re: If the sun were powered by gravitational collapse, how long would it last?

Date: Tue Jan 30 13:57:17 2001
Posted By: Donald Terndrup, Faculty, Astronomy, Ohio State University
Area of science: Astronomy
ID: 980144974.As

The Sun would only last about 20--30 million years
if gravitational collapse were its only source of energy.

Once upon a time, the sun did receive its energy this
way - this was during its formation, when it shrank from
about 2-3 times its current size to the size it has now.

At the end of this contraction, the temperatures in the
core of the sun became sufficiently high that hydrogen
began fusing into helium, providing an energy source that
lasts far longer than gravitational contraction.

The Sun would only need to shrink by 1-2 kilometers per
year to provide its luminosity from gravitational contraction.

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