Eta Carinae
This stellar system is currently one of the most massive that can be studied in detail. Until recently, Eta Carinae was thought to be the most massive single star, but in 2005 it was proved to be a binary system. The most massive star in the Eta Carinae multiple star system probably has more than 100 times the mass of the Sun. There are other massive stars which are known to be more luminous and are more massive.