A classification of stellar spectra according to luminosity for a given spectral type. The luminosity class is an indication of a star's surface gravity. It is shown by a Roman numeral as follows: I (
supergiants), II (bright giants), III (normal giants), IV (subgiants), and V (dwarf stars, or main-sequence stars). Luminosity classes VI (subdwarfs) and VII (white dwarfs) are rarely used. Subclasses a, b, and c are especially used for supergiants, while the most luminous hypergiants are assigned luminosity class Ia-0.
Number distribution of stars or galaxies (galaxy) with respect to their absolute magnitudes. The luminosity function shows the number of stars of a given intrinsic luminosity (or the number of galaxie
s per integrated magnitude band) in a given volume of space.
A high-luminosity variable star, which represents a transition phase in the life of a massive star when it evolves off the main sequence to become a supernova. Only about a dozen confirmed luminous bl
ue variable stars are presently known in our Galaxy.
A high-luminosity variable star, which represents a transition phase in the life of a massive star when it evolves off the main sequence to become a supernova. Only about a dozen confirmed luminous bl
ue variable stars are presently known in our Galaxy.
A high-luminosity variable star, which represents a transition phase in the life of a massive star when it evolves off the main sequence to become a supernova. Only about a dozen confirmed luminous bl
ue variable stars are presently known in our Galaxy.