Supernoovade vaatlemine tugineb asjaolule, et Ia tüüpi supernoovade absoluutset heledust saab võrdlemisi täpselt hinnata - I a tüüpi supernoovad on n-ö standardküünlad.
A standard candle is a class of astrophysical objects, such as supernovae or variable stars, which have known luminosity due to some characteristic quality possessed by the entire class of objects. Thus, if an extremely distant object can be identified as a standard candle then the absolute magnitude M (luminosity) of that object is known.'
