August 27, 2011

Astronomers Discover ‘Once In A Generation’ Supernova


A team of scientists has discovered a supernova closer to Earth than any of its kind in a generation.

Astronomers believe the supernova they caught, which is about 21 million light years away from Earth, is just within hours of its explosion.

Scientists around the world are scrambling to observe it with as many telescopes as possible, including the Hubble Space Telescope. 

Andy Howell, adjunct professor of physics at University of California - Santa Barbara (UCSB) and staff scientist at Las Cumbres Observatory Global Telescope Network (LCOGT), is one of the leaders of the team that discovered the cosmic phenomenon.

"We caught this supernova earlier than we've ever discovered a supernova of this type," Howell said in press release. "On Tuesday, it wasn't there. Then, on Wednesday, boom! There it was —— caught within hours of the explosion. As soon as I saw the discovery image I knew we were onto something big."

The supernova was discovered by the Palomar Transient Factory (PTF) survey, which is designed to observe and uncover astronomical events as they happen.

These supernovae can reach the brightness of over a billion suns in the first three weeks after the explosion, according to Howell. 

They normally cannot be seen so soon after the explosion because they are too faint. The closeness of the event was one factor that helped the astronomers make the discovery.

The supernova has been dubbed PTF 11kly and occurred in the Pinwheel Galaxy, which is located in the "Big Dipper".

"PTF 11kly is getting brighter by the minute," Peter Nugent, the senior scientist at Berkeley Lab who first spotted the supernova, said in a press release.

The team put in an urgent request on Wednesday to activate the Hubble Space Telescope.  The telescope's schedule is set weeks in advance, but was interrupted to insert regular observations of the new supernova.

Catching supernovae so close to Earth allows a rare glimpse at the outer layers of the supernova.

"Type Ia supernovae are the kind we use to measure the expansion of the universe. Seeing one explode so close by allows us to study these events in unprecedented detail," Mark Sullivan, the Oxford University team leader who was among the first to follow up on this detection, said in a press release.

Howell calls the stars that explode as Type Ia supernovae "zombie" stars because they are dead and come back to life by sucking matter from a companion star.

"When you catch them this early, mixed in with the explosion you can actually see unburned bits from the star that exploded: It is remarkable," said Howell. "We are finding new clues to solving the mystery of the origin of these supernovae that has perplexed us for 70 years. Despite looking at thousands of supernovae, I've never seen anything like this before."

The closeness of this supernova means that even amateur astronomers will be able to view it in coming weeks.

"The best time to see this exploding star will be just after evening twilight in the Northern hemisphere in a week or so," Sullivan said in a press release. "You'll need dark skies and a good pair of binoculars, although a small telescope would be even better."

The scientists in the PTF have discovered over 1,000 supernovae since it started operating in 2008.  The last time a supernova of this type occurred so close to Earth was in 1986.

"Before that, you'd have to go back to 1972, 1937 and 1572 to find more nearby Type Ia supernovae," said Nugent. "Observing PTF 11kly unfold should be a wild ride. It is an instant cosmic classic."

"Back then we didn't have modern instruments," noted Howell. "Now we have digital cameras, robotic telescopes, and all kinds of orbiting satellites that can see in x-rays, the ultraviolet, and visible light. We're going to have a field day."


Image 1: This image of PTF 11kly was taken Wednesday, Aug. 24, with the Las Cumbres Observatory Global Telescope Network telescope at UCSB's Sedgwick Reserve. The supernova, on the outskirts of the Pinwheel Galaxy (M101) has brightened dramatically in the one day it has been observable. Credit: BJ Fulton, LCOGT

Image 2: The arrow marks PTF 11kly in images taken on the Palomar 48-inch telescope over the nights of, from left to right, Aug. 22, 23, and 24. The supernova wasn't there August 22, was discovered Aug. 23, and brightened considerably by Aug. 24. Credit: Peter Nugent and the Palomar Transient Factory


On the Net: