Mass, luminosity, and the HR diagram

For many stars, it is possible to find the mass of the star. This isn't easy. We will discuss how to do it later.

What one finds for main sequence stars is that the luminosity is closely related to the mass. Here is a sketch. (It is not real data, but it is pretty close.)

Using this relation, we can label regions on the HR diagram according to the mass of the corresponding stars.

Our conclusion:

Different stars have different masses.
Among all stars with the same mass, almost all have the same properties.
The most massive stars are the most luminous.

Davison E. Soper, Institute of Theoretical Science, University of Oregon, Eugene OR 97403 USA soper@bovine.uoregon.edu