Brightest Stellar Event in History

From: My Interesante What has been the Brightest Stellar Event in History? http://www.muyinteresante.es/icual-ha-sido-el-evento-estelar-mas-brillante-de-la-historia

The supernova or stellar explosion that occurred between April 30 and May 1 in 1006 may have been the brightest interstellar event ever witnessed on Earth. It was observed and recorded by different communities of scientists around the world, including Chinese astronomers who documented that the astronomical event was visible for three years. The description was more explicit by an Egyptian astronomer who said that the phenomenon was about three times brighter than Venus, a light emission  equivalent to almost a quarter of the brightness of the moon. 

Now an international team led by researchers at the Astrophysics Institute of the Canary Islands (IAC) and the University of Barcelona (UB) recently discovered that the event was probably caused by the collision of two white dwarfs . White dwarfs stars in the last stage of his life when they have run out of fuel and are slowly cooling down. The SN1006 supernova belongs to the type that occur in binary star systems, which consist of two astronomical objects bound together by their gravitational pull. These systems can consist of a white dwarf and a companion star from which the dwarf star strips away additional matter. When this contribution of matter achieves a critical mass 1.4 times the mass of the Sun, called the Chandrasekhar limit mass, the white dwarf collapses ejecting its outer material in a massive supernova explosion.  Another possibility is that this system was composed of two white dwarfs that merge together to create the massive supernova observed here on Earth. 

Supernovae are exploding stars that occur in the last stage of their lives.  They emit a lot of energy and eject a huge amount of material at high speed into interstellar space. The supernova that occurred in 1006 was probably produced by a thermonuclear explosion of a white dwarf that reached the Chandrasekhar mass limit due to the merger with another white dwarf binary system. The final clue leading researchers to conclude that this event was caused by the merger of two white dwarfs was that this supernova, about 7,000 light years from Earth, does not have a companion star to the white dwarf progenitor. The explosion produced by the merger of two white dwarfs, in fact, left of a companion star.  Only a supernova remnant that can be studied until centuries later.  The supernova of 1006, is one of only four historical supernovae of this type that occurred in the Milky Way