Astronomers have discovered a previously unknown birthplace of some of the universe’s rarest elements: a giant flare unleashed by a supermagnetized star. The astronomers calculated that such flares could be responsible for forging up to 10% of our galaxy’s gold, platinum and other heavy elements.

The discovery also resolves a decades-long mystery concerning a bright flash of light and particles spotted by a space telescope in December 2004. The light came from a magnetar—a type of star wrapped in magnetic fields trillions of times as strong as Earth’s—that had unleashed a giant flare.

The powerful blast of radiation only lasted a few seconds, but it released more energy than the sun does in 1 million years. While the flare’s origin was quickly identified, a second, smaller signal from the star, peaking 10 minutes later, confounded scientists at the time. For 20 years, that signal went unexplained.