Stellar Lifetimes
•The Sun (and all stars) will eventually run out of
fuel (hydrogen in regions where it is hot enough
for fusion).
•If all the hydrogen in the Sun could fuse to helium,
the Sun’s lifetime would be 100 billion years.
•But, by the time about 10% of the Sun’s H has
been converted into He the solar structure will be
changed and it will not be a main-sequence star.
