Ia超新星
Type Ia supernova events occur when a white dwarf star accretes enough additional matter to exceed the Chandrasekhar limit and collapses, triggering runaway fusion and a supernova explosion. Because this collapse happens at a consistent mass, the resulting explosions have very uniform characteristics, and are used as "standard candles" to measure the distance to their host galaxies. The exact brightness and behavior of a Type Ia supernova depends on the metallicity of its parent star (the fraction of the star composed of elements heavier than hydrogen and helium before its evolution into a white dwarf). Because the SN 2011fe event was detected so early, astronomers can gain a more accurate measurement of its initial composition and of its evolution during the supernova explosion, and so refine their models of Type Ia supernova events, resulting in more precise distance estimates for other Type Ia supernova observations.