- apparent brightness
- a measure of the amount of light received by Earth from a star or other object—that is, how bright an object appears in the sky, as contrasted with its luminosity
- brown dwarf
- an object intermediate in size between a planet and a star; the approximate mass range is from about 1/100 of the mass of the Sun up to the lower mass limit for self-sustaining nuclear reactions, which is about 0.075 the mass of the Sun; brown dwarfs are capable of deuterium fusion, but not hydrogen fusion
- color index
- difference between the magnitudes of a star or other object measured in light of two different spectral regions—for example, blue minus visual (B–V) magnitudes
- giant
- a star of exaggerated size with a large, extended photosphere
- luminosity
- the rate at which a star or other object emits electromagnetic energy into space; the total power output of an object
- magnitude
- an older system of measuring the amount of light we receive from a star or other luminous object; the larger the magnitude, the less radiation we receive from the object
- proper motion
- the angular change per year in the direction of a star as seen from the Sun
- radial velocity
- motion toward or away from the observer; the component of relative velocity that lies in the line of sight
- space velocity
- the total (three-dimensional) speed and direction with which an object is moving through space relative to the Sun
- spectral class
- (or spectral type) the classification of stars according to their temperatures using the characteristics of their spectra; the types are O, B, A, F, G, K, and M with L, T, and Y added recently for cooler star-like objects that recent survey have revealed
