Archive of Astronomy Questions and Answers

What is Eta Carina?

Eta Carina is several million times brighter than the Sun, and one hundred times as massive. The superstar, located 8,000 light-years away underwent a colossal outburst 150 years ago. Radio and X-ray astronomers have recently detected smaller outbursts in gas around the star. It is definitely a dynamic object with changes occurring monthly. Some speculate that it is getting ready for some titanic outburst in the next few thousand years. The total range in brightness suggests a nova-like object rather than a supernova. In fact Eta Carina is regarded as a 'slow nova' based on the long duration of its brightness increase prior to the 1843 event, and it's maximum lasted 35 years rather than a few months as is normal fo novae. In 1843 it was probably the most luminous object in the entire Milky Way. In 1965, Fritz Zwicky put Eta Carina in a new class of supernovae 'Class V : High luminosity ejection variables'.

This star has been frequently studied with the Hubble Space Telescope and there are some exciting images over at their Eta Carina Site. Previous HST observations found that the gas from the earlier giant explosion now forms a bizarre double-lobed nebula pinched in the center by a ragged equatorial disk. The gas was ejected along the equatorial plane of Eta Carina about 100 years ago. Moving outward at about 100 thousand miles per hour, the gas is now about 60 billion miles, (100 billion kilometers), or 700 times the distance between Earth and the Sun. The most recent study has detected ultraviolet LASER emission from this star.