Astronomers watch supernova go bang

Detailed, real-time data

Scientists have, for the first time, been able to watch a star go supernova in real time, thanks to NASA's Swift satellite.

The event began back in February, when the Swift satellite, designed to detect and respond to a gamma ray burst (GRB) within 20 to 70 seconds, first sounded the alarm. The burst it had spotted lasted much longer than normal, continuing for around 40 minutes. Because of this, the observatory was able to capture data using all three of its instrument sets.

Swift carries three instruments: the Burst Alert Telescope (BAT), the X-Ray telescope, and the Optical and UV telescope. Each one gives astronomers more accurate data to help pinpoint the source of gamma rays. The satellite also alerts other orbital and ground based observatories, so they can view the event too.

"This GRB was the most extraordinary evolving object yet seen by Swift," said Dr Paul O'Brien from the University of Leicester.

This burst was also much closer than normal, and the researchers identified it as originating in a star-forming galaxy about 440m light years away, towards the constellation Aries. The team soon realised they were witnessing the first stages of the death of a star.

Dr O'Brien continued: "The three on-board telescopes all detected a slowly brightening then fading object. The results suggest a broad jet expanded into the surroundings, but it was accompanied by a slower-moving and incredibly hot - two million degree - bubble of gas produced from the shock-wave of the exploding star."

Dr Andrew Levan, University of Hertfordshire, said: "As well as studying the early evolution of the supernova for the first time these observations also show how the material ejected in the explosion evolve in the following days and weeks, the timescales on which supernovae are normally studied."

The observations revealed that this supernova was brighter than most, but dimmer than those usually associated with gamma ray bursts.

A gamma ray burst is associated either with the collapse of a massive star or with the collision of two stars. The bursts are normally very short lived - lasting from less than a second to just a few minutes.

Dr Levan said understanding the behaviour of this "transition object" would help scientists understand what it is about a star that produces a gamma ray burst.

"Usually these events are not detected until after the supernova has brightened substantially in the optical wavelength, many days after the initial explosion," said Professor Keith Mason, UK lead investigator for the UV telescope on Swift and CEO of the Particle Physics and Astronomy Research Council [PPARC].

"On this occasion we were able to study the remarkable event in all its glory from the very beginning." ®

An animation of the event is available here.

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