Stars: Properties and Classification

Another (more accurate) method to
measure Temperatures in Stars
Using spectra (recall the Fraunhofer spectrum of the Sun):
The `dark lines are created when the atoms in the photosphere
have energy levels that match the photons that are emitted
from the star.
1. They `reveal the composition of the star.
2. The strength of the lines (how `dark they are) depend on
the stars surface temperature.