Astronomers have, for the first time ever, watched live as a star blew itself to bits.

They witnessed a spectacular light-show called a supernova in a distant galaxy, 440 million light years from Earth.

International scientists, including a UK team, used Nasa’s Swift satellite plus observatories on Earth to catch the blast. The death star briefly became as bright as all the stars in the Milky Way combined.

Astronomers were alerted to the catastrophic event by a sudden burst of gamma rays from a star-forming galaxy in the constellation of Aries on February 18. They immediately realised that this was an unusual gamma-ray burst (GRB), about 25 times closer and 100 times longer than most observed.

Because the burst was so long Swift was able to observe the bulk of the explosion with all three of its instruments: the Burst Alert Telescope, which detected the burst and relayed the location to ground observatories within 20 seconds; the X-ray telescope and Ultraviolet/Optical Telescope.

“This GRB was the most extraordinary evolving object yet seen by Swift,” said team member Dr Paul O’Brien at the University of Leicester. “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 O’Brien added: “This is the first time such an extraordinary event has been seen from a GRB.”

Other UK astronomers from the Universities of Leicester and Hertfordshire used giant telescopes in Chile and California to track the bubble of gas and debris blown out by the supernova.

The picture is a frame from an animation of a gamma-ray burst as a star collapses on itself, produced by Nasa artist Dana Berry.