The Main Sequence
A Hertzsprung-Russell diagram plots the actual brightness (or absolute magnitude) of a star against its color index (represented as B-V). The main sequence is visible as a prominent diagonal band that runs from the upper left to the lower right. This plot shows 22,000 stars from the Hipparcos Catalogue together with 1,000 low-luminosity stars (red and white dwarfs) from the Gliese Catalogue of Nearby Stars. /via Wikipedia
