Abstract
Stars with masses greater than 8 solar masses have a very short life on the main sequence, and then burn helium, followed by carbon, oxygen, etc., until they have a core of iron and silicon. Fusion continues in shells, until the core implodes and the entire envelope is explosively expelled, releasing heavy elements and enriching the interstellar medium. If the residue exceeds 3 solar masses, it collapses into a black hole. Some of these can be detected if they have retained their companion in a binary.
