Mystery explosion detected in distant galaxy
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An unexplained explosion has been discovered in the deepest X-ray image of our universe ever taken.

The galaxy in which the event occurred, which is situated 10.7 billion light years away, had seemed relatively unremarkable until October 2014 when it suddenly became 1,000 times brighter.

The anomalous event, which lasted only a few hours, left astronomers scratching their heads.

"We may have observed a completely new type of cataclysmic event," said researcher Kevin Schawinski from the Swiss Federal Institute of Technology in Zurich.

"Whatever it is, a lot more observations are needed to work out what we're seeing."

One possibility is that the event could have been a gamma-ray burst - a high-energy explosion typically caused by a massive star collapsing or by the merging of two neutron stars.

Gamma-ray bursts are usually picked up when they are pointing towards the Earth, but if one happened to be pointing away from us then it may account for these new observations.

It is also possible that the event was caused by a black hole shredding a white dwarf star.

"None of these ideas fits the data perfectly," said researcher Ezequiel Treister.

"But then again, we've rarely if ever seen any of the proposed possibilities in actual data, so we don't understand them well at all.