Monday, July 25, 2011

Eta Carinae

The hypergiant star, Eta Carinae, is probably the most amazing star that astronomers have ever studied. The stellar system in the constellation Carina is believed to be binary, with its central, and most massive, star being more than 100 times more massive than the sun. Eta Carinae is between 7,500 and 8,000 light years from earth and could be the only hypergiant in our galaxy. So far, it is the only hypergiant that we are able to study in great detail because it is relatively close.
Carina nebula, Eta Carinae is the dense white ball centered to the left (1/5 of the way from left)

Super massive stars, like Eta Carinae, are extremely bright. This star happens to be about 4,000,000 times brighter than the sun. The reason for this is that hypergiants burn much brighter due to their great mass. Our sun can only burn so fast because it is only so massive, but Eta Carinae is so much larger. It is able to burn extremely fast and extremely bright. The brightness of this star does tend to fluctuate however. In 1843, it was observed that Eta Carinae had experienced a supernova impostor event. Over several years, the star had emitted as much light as a supernova without actually going supernova. Eta Carinae survived the explosion which was most likely caused by the tenuous struggle between gravity and the fusion reaction. The star hasn't fully recovered from this massive explosion, even though it has been over 150 years.
Eta Carinae created these lobes and center disc after its supernova impostor event

Three structures have been created around Eta Carinae by the incredibly powerful solar winds that come from the star. The central regions of these structures can be as hot as 60 MK (Megakelvin, or million Kelvin) while the outer horse-shoe region is 3 MK.
Eta Carinae has created superheated structures with solar emissions

The more massive a star is, the faster it burns itself out. Our sun will live for another 5 billion years, but Eta Carinae could go hypernova within the next million years, if not sooner. Stars like Eta Carinae are so massive that they go beyond supernovae when they die, creating something called a hypernova, probably the largest explosion possible in our universe. Once Eta Carinae goes hypernova, it will most likely collapse into a massive black hole, ejecting tight beams of gamma radiation, called gamma ray bursts, from its rotational poles. If this burst were to hit earth, it would be equivalent to one kiloton of TNT being detonated over every square kilometer over the entire hemisphere hit. The chances of this are very small however, the poles of the star are not currently pointed at us, and these tight beams have the entirety of the universe, so the chances of them hitting such a small target are incredibly slim. We will most likely be fine when the radiation from the hypernova reaches us, but the death of Eta Carinae will be spectacular. It is very possible that the light given off from the explosion will be enough to read by at night. Eta Carinae is the blazing king of the stars, reigning superior, but its life shall be short. It is very possible that it has already met its end. Being so far away, Eta Carinae could go hypernova today, and we wouldn't know for 7,500 years. One thing is for sure though, when Eta Carinae finally does die, it will die with glory.
Depiction of high energy laser beams being emitted from Eta Carinae

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