Standard Candle

Astronomical object with a known absolute magnitude. They are extremely important to astronomers since by measuring the apparent magnitude of the object we can determine its distance. The most commonly used standard candles are Cepheid variable stars and RR Lyrae stars. In both cases, the absolute magnitude can be determined from its variability period. Type Ia supernovae are also considered standard candles, but more correctly they are standardizible candles since they do not all have the same peak brightness. However, differences in peak luminosities correlate with how quickly the light curve declines after maximum light via the Type Ia supernova luminosity-decline rate relation, and can be made into standard candles by correcting for this effect.