Berkeley scientists this week discovered a new supernova, closer to Earth than any seen in the last 40 years, and believe they've spotted it within hours of its explosion.
Astronomers are now scrambling to observe it with as many telescopes as possible, including the Hubble Space Telescope, and it's likely to remain a major target for research for the next decade or more.
Dubbed PTF 11kly, the supernova is about 21 million light-years away in the Pinwheel Galaxy, in the Ursa Major constellation. It was discovered by the Palomar Transient Factory (PTF) survey, which uses a robotic telescope mounted on the 48-inch Samuel Oschin Telescope to scan the sky nightly.
"We caught this supernova very soon after explosion. PTF 11kly is getting brighter by the minute. It's already 20 times brighter than it was yesterday," says Peter Nugent, the senior scientist at Berkeley Lab who first spotted it.
"Observing PTF 11kly unfold should be a wild ride. It is an instant cosmic classic."
Within 12 hours of its discovery, PTF 11kly had been observed by other telescopes around the globe, and it was found tobelong to the Type Ia category. Indeed, this is the earliest spectrum ever taken of a Type Ia supernova.
"Type Ia supernova 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," says Mark Sullivan of Oxford University, one of the first to follow up on the discovery.
The Hubble Space Telescope will begin studying the supernova's chemistry and physics this weekend.
"When you catch them this early, mixed in with the explosion you can actually see unburned bits from star that exploded! It is remarkable," says Andrew Howell of UC Santa Barbara/Las Cumbres Global Telescope Network.
"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 supernova is still getting brighter, and may even be visible with good binoculars in ten days' time.
"The best time to see this exploding star will be just after evening twilight in the Northern hemisphere in a week or so," says Sullivan. "You'll need dark skies and a good pair of binoculars, although a small telescope would be even better."
PTF scientists have discovered more than 1,000 supernovae since it started operating in 2008 - but say this could be their most significant discovery yet. The last time a supernova of this sort occurred so close was in 1986, but that one was peculiar and heavily obscured by dust.
"Before that, you'd have to go back to 1972, 1937 and 1572 to find more nearby Type Ia supernovae," says Nugent.