Stellar Magnitudes

More revealing than apparent magnitude is absolute magnitude, which is the apparent magnitude a star would have if it were ten parsecs from the Earth (a parsec is a unit of distance equal to 12 trillion mi [19 km]). This is important because apparent magnitude can be deceiving. You know that a lit match is not as bright as a streetlight, but if you hold the match next to your eye, it will appear brighter than a streetlight six blocks away. That's why V is called apparent magnitude: it is only how bright the star appears to be. For example, the Sun is a fainter star than Sirius! Sirius emits far more energy than the Sun does, yet the Sun appears brighter to us because it is so much closer. Absolute magnitude, however, reveals the truth: the Sun has an absolute magnitude of +4.8, while Sirius is +1.4 (remember, smaller numbers mean brighter, not fainter).