Star dies in brightest supernova

A massive star around 150 times the size of the Sun has exploded in what is the brightest supernova ever seen, Nasa scientists have said.
Supernovae occur when huge, mature stars effectively run out of fuel and collapse in on themselves.
But scientists believe this one was obliterated in an explosion which blasted all its material into space.
And astronomers say a star in our own Milky Way galaxy could be about to perform the same celestial fireworks.
The supernova star, called SN 2006gy, was originally discovered in September last year.
The explosion peaked for about 70 days, during which it is thought to have shone about five times more brightly than any supernova seen in the past.
"Of all exploding stars ever observed, this was the king," Alex Filippenko, one of the Nasa-backed astronomers observing the phenomenon, said.
'Monstrous explosion'
Nathan Smith, who led a joint team from the University of California at Berkeley and the University of Texas in Austin, said it was a "truly monstrous explosion, a hundred times more energetic than a typical supernova".
"That means the star that exploded might have been as massive as a star can get, about 150 times that of our sun. We've never seen that before."
Eta Carinae's explosion could be the best star-show in the history of modern civilization
Mario Livio
He said the star, which is 240 million light years away, polluted the surrounding environment with metals and elements that are needed for life.
Scientists say that the star which exploded is similar to Eta Carinae, an enormous star in our own Milky Way.
They say that before the supernova SN 2006gy expelled a large amount of material, similar in mass to Eta Carinae, prompting speculation that a similar fate awaits Eta Carinae.
Dave Pooley, at the University of California at Berkeley, said if Eta Carinae were to explode "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."
He added there has not been a supernova in the Earth's Milky Way galaxy for more than 400 years.
Mario Livio, of the Space Telescope Science Institute in Baltimore, said that Eta Carinae could explode at any time.
"This could happen tomorrow, it could happen 1,000 years from now," he told the Reuters news agency.
"Eta Carinae's explosion could be the best star-show in the history of modern civilization," he said.