Analyzing Starlight

apparent brightness

A measure of the amount of light received by Earth from a star or other object, indicating how bright it appears in the sky.

brown dwarf

An object intermediate in size between a planet and a star, typically about 1/100 to 0.075 times the mass of the Sun, capable of deuterium fusion but not hydrogen fusion.

color index

The difference between the magnitudes of a star measured in two different spectral regions, such as blue minus visual (B–V) magnitudes.

giant

A star of exaggerated size with a large, extended photosphere.

luminosity

The rate at which a star emits electromagnetic energy into space; the total power output of the star.

magnitude

An older system for measuring the light received from a star; larger magnitudes correspond to less received radiation.

proper motion

The angular change per year in the direction of a star as observed from the Sun.

radial velocity

Motion of an object toward or away from the observer; the component of velocity in the line of sight.

space velocity

The total speed and direction an object is moving through space relative to the Sun.

spectral class

The classification of stars according to their temperatures based on their spectral characteristics, including types O, B, A, F, G, K, M, L, T, and Y.