Illustration of a star exploding as a supernova. Photo: NASA.

72 flashes recorded as bright as a supernova.

Flashes were much briefer than typical supernovae.

Up to 30 billion kilometres across in size.

A team of astronomers found 72 bright flashes of light in deep space four billion light years away, and have no idea what it means.

Miika Pursiainen of the University of Southampton presented the new results on Tuesday April 3 at the European Week of Astronomy and Space Science.

His team were examining data in a global effort to better understand dark energy and its role in the expansion of the universe.

Using a large camera on a 4-metre telescope in the Cerro Tololo Inter-American Observatory in the Chilean Andes to search for supernova explosions which can “briefly be as bright as a whole galaxy”, they instead found 72 flashes like this one:

Picture: Miika Pursiainen/University of Southampton

That particular series was photographed over 26 days.

The events were similar to supernovae in terms of brightness, and like a supernova, they appeared to be expanding and cooling over time. But supernovae typically last “for several months or more”, the team said.

The flashes were hot – between 10,000C and 30,000C – and ranged in size from around 300 million kilometres to up to a hundred times larger.

One possible explanation is the team were not actually seeing the star itself explode. Rather, as it got hotter, the star was heating material it had shed in the lead-up to its own demise.

“The DES-SN survey is there to help us understand dark energy, itself entirely unexplained,” Pursiainen said. “That survey then also reveals many more unexplained transients than seen before.”

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