Scientists witness birth of supernova

Massive explosion 1b light years away

LONDON - Scientists have for the first time witnessed the flash of light produced inside a dying star just before it explodes, according to a study published yesterday that provides a unique glimpse into how a supernova forms.

The red super giant, more than 500 times more massive than the Earth's sun, was destroyed after its core collapsed and a shock wave of energy blew it up, the astronomers said.

Until now, scientists have only been able to observe the afterglow of such bursts without knowing which star actually exploded, the researchers reported in the journal Science.

"We have witnessed the violent death of a massive star in a galaxy almost one billion light years away in unprecedented detail," Kevin Schawinski, an astronomer at the University of Oxford who led the study, said in a telephone interview.

"We caught the star while the supernova shock wave approached the surface of the star and then blew it apart."

A light year is the distance light travels in a year.

The researchers used images from a satellite pointed to where telescopes on Earth had detected supernovae.

They expected a first flash from inside a dying star to only be visible in ultraviolet light from space.

After the satellite produced images of a seven-hour flash, the researchers sifted through data taken from telescopes in Hawaii fixed to the same coordinates that later confirmed a supernova formed in that precise location, said Stephen Justham, a University of Oxford astronomer who worked on the study.

"The flash began just hours before the star was disrupted," he said. "How the shock wave travels in a star tells us the size of the star and what the inside is like in its final moments. The longer the flash, the bigger the star."