Supernova discovery sheds new light on lives of giant stars

BERKELEY, Calif., May 21 (UPI) -- For the first time, scientists are locating and observing supernovas in great detail. And in one case, they've been able to determine which type of star was responsible -- a Wolf Rayet star.

"It's better to burn out than to fade away," Neil Young famously sang. Wolf-Rayet stars took the words to heart. The brightest stars in the universe don't go quiet in the night, but explode with a burst of fiery light briefly outshines their entire galaxy.

Wolf Rayets burn five times as hot as the sun and are twenty times as large. Their deaths are even more terrific. They're also mysterious.

These fantastic star deaths are so bright, so powerful, that they are difficult to see, the explosion of light and matter shot out into the universe obscures the source of the explosion.

For this reason, astronomers have long been fuzzy on exactly how Wolf-Rayet stars come to self-destruct. And some have even questioned whether Wolf-Rayet stars are responsible for the deathly explosions known as supernovas.

New observation techniques for spotting and studying supernovas, however, are helping to shed some light on the mystery.

"For the first time, we can directly point to an observation and say that this type of Wolf-Rayet star leads to this kind of Type IIb supernova," said Peter Nugent, head of the Berkeley Lab's Computational Cosmology Center.

Nugent and a team of astronomers recently located a Type IIb supernova called SN 2013cu that originated from the Bootes constellation, about 360 million light years away from Earth. They found it with the help of the Palomar Transient Factory, a robotic telescope that constantly scans the skies for supernova-like explosions.

By studying the supernova so quickly after it happened, astronomers gathered a wealth of detailed information.

"Newly developed observational capabilities now enable us to study exploding stars in ways we could only dream of before," said Dr Gal-Yam, author of the supernova study published in the journal Nature this week. "We are moving towards real-time studies of supernovae."

Dr. Gal-Yam and his fellow scientists at the Weizmann Institute, in Israel, then applied a new analysis technique called flash spectroscopy, which determine the makeup of the exploded star.

The evidence suggested the Type IIb supernova was the result of a dying Nitrogen-rich Wolf-Rayet. This is the smoking gun," Nugent concluded.