How do people know how old a star is?

Wow, this is a popular question! Scientists look at the mass, temperature, spectrum, and luminosity to figure out the age of a star. But the composition of the star is also very important.

Stars burn hydrogen to make energy. Once the hydrogen us used up it burns helium. Stars start out as main sequence stars. When they start burning helium they get bigger and are called giants. Look on the Hertzsprung-Russell Diagram to learn more.

Scientists can look at the temperature and spectra to tell how much hydrogen or helium is left in the star. This tells them how old the star is!

Submitted by Dana, Kelly, Michael, Kelli, Tommy, Nick, Randall, (ages 11 &12, North Carolina)
(3/10/00)

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Last modified prior to September, 2000 by the Windows Team

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