Wednesday, August 26, 2015

Supernova

A supernova occurs when a star explodes. From the earth, people can see a new start appear in the sky and then fade over months back to invisibility.

Such explosion can be exploded can be caused by a massive star near the end of its life collapsing into a black hole or neutron star or a dead star; a white dwarf, collapsing into a neutron star.

At the turn of the 19th century, the binary star system Eta Carinae was faint and undistinguished.

In the first decades of the century, it became brighter and brighter, until, by April 1843 when it was exploded. The blast spat matter out at nearly 2.5 million kilometers an hour, and was so bright that it was thought to be a supernova explosion.

The larger of the two stars in the Eta Carinae system is a huge and unstable star that is nearing the end of its life.

The event observed in the 19th century was a stellar near-death experience. Scientists call these outbursts supernova impostor events, because they appear similar to supernovae, but stop just short of destroying their star. In 2004, an explosion thought to be similar to the 1843 Eta Carinae event was seen in a galaxy over seventy million light years from the Milky Way. Just two years later, the star exploded as a supernova.

Today nearly 300 supernova remnants are known, the majority having estimated ages from several thousand to several hundred thousand years.

Six supernova explosions have been witnessed with naked eye in historical times, many being recorded by Chinese astronomers, like the Crab nebula in AD 1054.

The first was recorder in AD 185 and the last appeared in 1987 in the Large Magellanic Cloud.  A neutrino burst from a supernova in the Large Magellanic Cloud was observed in the proton decay detectors Kamiokande and IMB on February 23, 1987. This supernova originated 160,000 light years from earth.

Two more are known to have ex0loded in the Milky Way during historic times) around 1671 and 1870), but were not seen because of the high interstellar dust obscuration.
Supernova

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