Cepeids vary in brightness because they are unstable, and actually shrink and grow.
To see this, click to view a NASA
animation of a cepheid variable star.
One more journey before you return to the lab to measure the age of the universe. A more detailed account of cephiad variable stars can be found at the MAP site we visited earlier. Thanks to the power or the internet, you are just a click away.
Check out your progress!
