Eta Carinae

Eta Carinae, also known as Tseen She and Foramen, is a system in the Carina constellation. It is about 8,000 light years from the Sun. It is known to contain at least two stars, one of which is a luminous blue variable star. It has combined luminosity of about four million times solar and an estimated system mass in excess of 100 solar masses. You can not see it north of 30°N latitude and it is circumpolar south of 60°S latitude. Based on its mass and stage of life, it is expected to go supernova in the astronomically near future.

This stellar system is currently one of the most massive that can be studied in great detail. It was thought to be the most massive single star until recently, when it was discovered to be a binary system. The most massive star in this multiple star system has less than 100 times the mass of the Sun. Stars in the mass class of E. Carinae produce more than a million times as much light as the Sun. They are quite rare — only a few dozen in the Milky Way. They are assumed to approach the Eddington limit( a star where the outward pressure of its radiation is almost strong enough to counteract gravity). Stars that are more than 120 solar masses exceed this limit, and their gravity is barely strong enough to hold in their radiation and gas. The system’s chief significance for astrophysics is its giant eruption or supernova imposter event, which was observed around 1843. During that event the system produced almost as much visible light as a supernova explosion, but it survived. The supernova impostor phenomenon may represent a surface instability or a failed supernova. This giant eruption was the prototype for this phenomenon, and after 160 years the star’s internal structure has not fully recovered.

When the system was first cataloged in 1677 it was of the 4th magnitude, but by 1730, observers noticed it had brightened considerably and was one of the brightest stars in Carina. It dimmed again and by 1782 it appeared to have reverted to its former obscurity. In 1820, it was observed growing in brightness again. By 1827, it had brightened more than tenfold and reached its greatest apparent brightness in April 1843. With a magnitude of ?0.8, it was the second brightest star in the night-time sky. It has since faded into the background, somewhat. Stars with such super luminosity tend to use up all of there energy source relatively quickly. The same is true here. The system is projected to explode in supernova or hypernova in less than one million years.

Here is the NASA webpage about the system. Here on Universe Today we have a great article about the impending death of the system. Astronomy Cast offers a good episode about nebulae.

References:
http://stars.astro.illinois.edu/sow/etacar.html
http://en.wikipedia.org/wiki/Eta_Carinae

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