luminosity class

lumnosity classes

Luminosity class is a classification of stellar spectra according to luminosity for a given spectral type; it was introduced as part of the Morgan-Keenan classification. The luminosity class broadly indicates whether a star is a dwarf (that is, a main sequence star), a giant, or a supergiant, since luminosity is directly related to surface area. Luminosity class is expressed as a Roman numeral, from I to V, and appears after the spectral type; for example, Tau Ceti, with spectral type G8, is listed as a G8V object.


Luminosity class Description
Ia-0 Hypergiant (extreme supergiant)
Ia Bright supergiant
Iab Normal supergiant
Ib Subluminous supergiant
II Bright giants
III Normal giants
IV Subgiant
V Main-sequence (dwarf) star