Scientists just observed the largest supernova in recorded history, PBS reports.
Discovered in June 2015 by ASAS-SN’s twin 14-centimeter telescopes operating in Cerro Tololo, Chile, the supernova just appeared as a transient dot of light in an image, and wasn’t immediately recognized as particularly special. Only after several other telescopes piled on to provide additional observations of the outburst’s fading afterglow did it become clear to Dong and his collaborators that they had seen something record-breaking. The first hint came from a spectrum of the supernova delivered by the 2.5-meter du Pont Telescope in Chile seven days after the initial discovery. “When we saw the spectrum, we were baffled,” Dong recalls. “It didn’t look like any supernova we had seen.
If ASASSN-15lh’s parent star shed its out layers of gas and then collapsed its inner core to form what’s called a magnetar—a dense, rapidly rotating magnetized core—then magnetized wind emanating from that collapse could have shocked the outwardly flying matter enough produce a massive explosion. The catch is that the magnetar would have to have been spinning at a rate of one revolution per millisecond—that’s 60,000 rpm—which pushes the boundaries of what scientists think is physically conceivable. The magnetar idea may not be correct, but it’s at least plausible. Meanwhile, experts are on the lookout for other explanations.