Chandra, the venerable orbiting X-ray telescope, just caught a big explosion 10 billion light-years away in an image called the Chandra Deep Field-South. But it came just as quickly as it went, and now astronomers are trying to figure out what it might have been.

The image is the "deepest X-ray image ever obtained," according the Chandra team. While it has been staring at this region of the sky repeatedly over the last 17 years, it's been only in the last three years that any X-ray activity at all was detected in this region.

X-ray images typically signify black hole activity and other energetic events that don't appear in visible light. This particular event exploded 1,000 times brighter than any prior observations, but within a day, it was gone.

It's likely a gamma ray burst with a few possible origins. The event, called CDF-S XT1, could be a neutron star merger, a massive star collapsing into a black hole or other compact object, or an intermediate mass black hole (a black hole between 100 and 1 million times the mass of the Sun) consuming a white dwarf. No host galaxy has, of yet, been pinned down.

A paper on the explosion has been accepted in the Monthly Notices of the Royal Astronomical Society. A pre-print is available here.

Source: Chandra