Eta Carinae - Significance

Significance

This stellar system is currently one of the most massive that can be studied in great detail. Until recently, Eta Carinae was thought to be the most massive single star, but in 2005 it was realised 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. Other known massive stars are more luminous and more massive.

Stars in the mass class of Eta Carinae produce more than a million times as much light as the Sun. They are quite rare — only a few dozen in a galaxy as big as the Milky Way. They are assumed to approach (or potentially exceed) the Eddington limit, i.e., the outward pressure of their radiation is almost strong enough to counteract gravity. Stars that are more than 120 solar masses exceed the theoretical Eddington limit, and their gravity is barely strong enough to hold in their radiation and gas.

Eta Carinae's chief significance for astrophysics is based on its giant eruption or supernova impostor event, which was observed around 1843. In a few years, Eta Carinae produced almost as much visible light as a supernova explosion, but it survived. Other supernova impostors have been seen in other galaxies, for example the possible false supernovae SN 1961v in NGC 1058 and SN 2006jc in UGC 4904, which produced a false supernova, noted in October 2004. Significantly, SN 2006jc was destroyed in a supernova explosion two years later, observed on October 9, 2006. The supernova impostor phenomenon may represent a surface instability or a failed supernova. Eta Carinae's giant eruption was the prototype for this phenomenon.