The brightest exploding star yet seen should provide important clues about the early Universe. The vast supernova that blew up with at least 100 times more energy than a typical star in its death throes is by far the biggest event of its kind observed by astronomers and remained brighter than any other for three months.

Almost eight months after SN2006gy was first spotted, it is still as luminous as most supernovas at their peak, easily outshining its host galaxy 240 million light years from Earth. Observations with Nasa’s orbiting Chandra X-Ray Observatory and ground-based telescopes in California and Hawaii have shown that it was caused by the explosion of a star 100 to 200 times bigger than the Sun.

“This was a truly monstrous explosion,” said Nathan Smith, of the University of California, Berkeley, who led the research team. “The star that exploded might have been as massive as a star can get.” The observations, published in the Astrophysical Journal, offer insights into the early Universe, and into how the cosmos was “seeded” with elements vital for life.

Dr Smith said: “This forces us back to the drawing board to understand how the most massive stars die.” He added: “The fact that this thing is so bright, and stayed bright for a long time, makes our chances of detecting them in the early universe much better.”

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