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Massive Star Eta Carinae

Visible in this center of image is purple-tinted light reflected from the violent star Eta Carinae itself. Surrounding this star are expanding lobes of gas laced with filaments of dark dust.  Jets bisect the lobes emanating from the central star. Surrounding these lobes are red-tinted debris captured only by its glow in a narrow band of red light. This debris is expanding most quickly of all, and includes streaming whiskers and bow shocks caused by collisions with previously existing material.

Eta Carinae has a mass of approximately 150 times that of the Sun, and is about 4 million times brighter than the Sun, making it one of the most massive and most luminous stars known. Stars with more than 100 times the mass of the Sun are quite rare—only a few dozen in a galaxy as big as the Milky Way. They are assumed to approach the Eddington limit, i.e., the outward pressure of their radiation is almost strong enough to counteract gravity.

Eta Carinae experienced a giant eruption or supernova impostor event, which was observed around 1843.  For a few years, Eta Carinae produced almost as much visible light as a supernova explosion, but it survived.  

Because of their disproportionately high luminosities, very large stars such as Eta Carinae use up their fuel very quickly. Eta Carinae is expected to explode as a supernova or hypernova some time within the next million years or so. As its current age and evolutionary path are uncertain, however, it could explode within the next several millennia or even in the next few years.  LBVs such as Eta Carinae may be a stage in the evolution of the most massive stars; the prevailing theory now holds that they will exhibit extreme mass loss and become Wolf-Rayet Stars before they go supernova, if they are unable to hold their mass to explode as a hypernova.

It is possible that the Eta Carinae hypernova or supernova, when it occurs, could affect Earth, about 7,500 light years away. It is unlikely, however, to affect terrestrial lifeforms directly, as they will be protected from gamma rays by the atmosphere, and from some other cosmic rays by the magnetosphere. The damage would likely be restricted to the upper atmosphere, the ozone layer, spacecraft, including satellites, and any astronauts in space. Scientist Dave Pooley has claimed that when the star explodes, "it would be so bright that you would see it during the day, and you could even read a book by its light at night".

Eta Carinae is located in the Carina Nebula.

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