Star of Eta CarinaeEta Carinae is one of the heaviest and most luminous stars known. Its mass probably exceeds 100 solar masses, and the star is about 4 million times brighter than the Sun. Such a massive star has a comparatively short lifetime of about 1 million years; when measured in the cosmic timescale, Eta Carinae must have formed quite recently. This star is highly unstable and prone to violent outbursts. These outbursts are caused by the very high radiation pressure at the star's upper layers, which blows significant portions of the matter at the "surface" into space during eruptions that may rage for several years. Credit: ESO