This image shows a powerful explosion, orange dot at the center of the image, that repeated several times over the course of a day, The image, taken with ESO’s Very Large Telescope (VLT), allowed astronomers to determine that the explosion didn’t take place in the Milky Way but in another galaxy. European Southern Observatory via AP

CAPE CANAVERAL, Fla. — Scientists have discovered a gamma ray explosion outside our galaxy that’s not only exceptionally powerful, but also long-lasting.

Telescopes on Earth and in space — including Hubble — have teamed up to study the unique explosion of high-energy radiation first observed in July. Astronomers reported Tuesday it's unlike anything they've witnessed before.

The repeated bursts of gamma rays were detected over the course of a day, according to scientists. That’s highly unusual since these kinds of bursts normally last just minutes or even milliseconds — rarely no more than a few hours — as dying stars collapse or are torn apart by black holes.

Scientists said such a long and recurrent gamma ray explosion is puzzling — a cosmic whodunit, at least for now. More observations are needed to confirm its precise whereabouts.

The European-led team announced its findings in the Astrophysical Journal Letters in August.