Type Ia Supernovae as Standard Candles

Astronomers classify types of supernovae for different reasons. Type Ia supernovae are particularly useful because they can be used to measure distances to other galaxies. To be able to use Type Ia supernovae to determine distance, we must first determine their actual, or intrinsic, peak brightness from the data we receive in our observations.

There is a relationship between the peak brightness of a Type Ia supernovae and the rate at which it decreases in brightness that allows astronomers to fit templates (which are graphs with model light curves) to Type Ia supernova data. Using these templates astronomers can correct the light curve of a Type Ia supernova to determine its intrinsic peak brightness, which is expressed as the supernova’s absolute magnitude (M). Astronomers have determined that most Type Ia supernovae have about the same intrinsic peak brightness and absolute magnitude. For this reason, Type Ia supernovae are sometimes called standard candles.