The Main Sequence and the HR Diagram
Nino Chelidze, Idaho State University
The Hertzsprung - Russell diagram is a graph created by Ejnar Hertzsprung
and Henry Norris Russell in 1911-1913. Astronomers use it to classify stars
according to their luminosity, spectral type, color, temperature and evolutionary
stage. There are three very different types of stars; therefore the HR Diagram
has three main regions. Stars are born, undergo evolutionary stages, reach
the stable phase of hydrogen burning and stay in this stage for most of their
lifetime. Stable stars lie along the Main Sequence according to their mass.
After billions of years stars die. Evolution stages, spectral classification
and properties of main sequence stars will be discussed.