Stellar classification

Spectral (or stellar) classification is the process by which scientists define the size, composition and emissions of a star or other astronomical object.

The system begins with a series of letters followed by single digits that determines the star's heat and output. Additional symbols and abbreviations are added to further qualify special types of stars and other observable stellar phenomena associated with the body. This systems also covers size estimate for stars in the main sequence of their lives, as the relation between size and output are different in stars that go through a giant star phase, such as a red giant