Type Ia supernova in the Large Magellanic Cloud. NASA/ESA Hubble Space Telescope image showing the remains of a Type Ia supernova in a neighbouring galaxy called the Large Magellanic Cloud. A Type Ia supernova is formed from the death of a white dwarf star, which grows in size by siphoning material from a stellar companion until it reaches a critical mass and then explodes. The predictable brightness of Type 1a supernovae allows astronomers to measure the expansion of the universe.