What is the difference between absolute and apparent magnitude?
Apparent magnitute is how bright a star looks. Absolute magnitude is how bright it really is. The farther a star (or any light source) is, the dimmer it looks. There are methods of determining absloute magnitude based on combining apparent magnitude with distance determined by parallax, and/or red shift, color, spectrographic make up, other known standard stars (called Cepheid variables) that always have the same magnitude and telltale signatures. If astronomers know the distance, combining it with the apparent magnitude will give the absolute magnitude.
