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Class act supernova caught on telescope
Posted: 26 August 2011

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Berkeley astronomers have caught the rare event of a type Ia supernova just hours after its eruption, residing a short 21 million light years away from Earth in the Pinwheel Galaxy (M101) of Ursa Major, making it the closest type Ia supernova seen in decades. Catching a stellar explosion of this kind is a rarity and an opportunity that scientists have grabbed with both hands made possible with a specialised survey telescope and sophisticated computational tools.

These images show Type Ia supernova PTF 11kly, the youngest ever detected—over the past three nights. The left image taken on August 22 shows the event before it exploded supernova, approximately 1 million times fainter than the human eye can detect. The centre image taken on August 23 shows the supernova at about 10,000 times fainter than the human eye can detect. The right image taken on August 24 shows that the event is 6 times brighter than the previous day. In two weeks time it should be visible with a good pair of binoculars. Image Credit: Lawrence Berkeley National Laboratory/UC Berkeley.

The supernova, named PTF 11kly, was discovered by the Palomar Transient Factory (PTF) survey, an instrument designed to pin down astronomical events as they happen. The supernova is set to be a target of research for the next decade due to its proximity, making it one of the most extensively studied stellar explosions in history with the help of many telescopes such as the Hubble Space Telescope.

“We caught this supernova very soon after the explosion. PTF 11kly is getting brighter by the minute. It’s already 20 times brighter than it was yesterday,” says the senior scientist at Berkeley Lab at the University of California, Berkeley, Peter Nugent, who spotted the supernova. “Observing PTF 11kly should be a wild ride. It is an instant cosmic classic.”

The PTF survey carries out its task of scanning the sky with the use of a robotic telescope mounted on the 48-inch Samuel Oschin Telescope at Palomar Observatory, Southern California. As soon as the supernova was spied, data raced more than 400 miles to supercomputers at the National Energy Research Scientific Computing Center (NERSC) which worked at high speeds to uncover the rare event just in time. Within hours, the supercomputers had scanned through the delivered data, identifying the supernova candidate before divulging PTF 11kly’s coordinates to telescopes around the world for further investigation.

Just three hours after the supernova’s detection by the PTF, telescopes in the Canary Islands were trained on the flashy event, capturing light signatures, or spectra. A further twelve hours later saw a suite of telescopes including the Lick Observatory (California) and Keck Observatory come to the conclusion that this exciting event was no other than a type Ia supernova; a special type that had had its spectrum caught at the earliest opportunity.

“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,” says Mark Sullivan, the Oxford University team leader who was among the first to follow up on the detection. The current belief is that this type of supernova is created by a white dwarf that has pulled too much material onto itself, resulting a dramatic explosion. Because they also explode with the same absolute magnitude, we can calculate from their faintness how far away they are and use them as standard candles.

Using the Hubble Space Telescope, the team will be watching the supernova carefully over the next few weeks as it allows a rare glimpse of the ruptured star’s outer layers, containing information of what type of star blew itself apart. “When you catch them this early, mixed with the explosion you can actually see unburned bits from the star that exploded! It is remarkable,” says Andrew Howell of UC Santa Barbara and the Las Cumbres Global Telescope Network. “We are finding new clues to solving the mystery of these supernovae. Despite looking at thousands of supernovae, I’ve never seen anything like this before.”

As we speak, the supernova is getting brighter, possibly making it luminous enough to view with binoculars in ten days’ time, presenting itself as the brightest supernova of its kind in the last 30 years.

Read Astronomy Now’s night sky consultant’s guide on how best to observe PTF 11kly here.