Measuring distances to stars through stellar parallax.
Measuring distances to stars through the moving cluster method.
Astronomers measure the temperature of a star by looking at the star's color and its spectrum.
The apparent brightness of a star tells how bright it seems to us.
The luminosity of a star tells how bright it really is. The luminosity can be determined from the apparent brightness and the distance.
Using luminosity and temperature information from lots of stars, one learns something by constructing a Hertzsprung-Russell diagram.
To undetstand temperatures and luminosities, we found that we needed to know about the masses of stars.
Updated 24 Octobber 2007
Davison E. Soper, Institute of Theoretical Science, University of Oregon, Eugene OR 97403 USA