Astronomers have spotted an astonishingly bright explosion in the sky that doesn’t look like any supernova we have ever seen before. It became brighter than most known supernovae before fading extremely quickly, making it a new type of object the researchers have named “luminous fast coolers”, or LFCs.
Matt Nicholl at Queen’s University Belfast in the UK and his colleagues spotted the object, which is called AT2022aedm but nicknamed Adam, using the ATLAS network of telescopes in Hawaii, Chile and South Africa. They then took more measurements with other observatories around the world. In just nine days, Adam – which lies near the edge of a galaxy that is home to relatively old stars – became hundreds of billions of times as bright as the sun. It then faded almost completely within a month. We would expect a supernova that bright to fade to around half its peak brightness in the same time.
“It’s a combination of properties that don’t match any known kind of object we’ve seen before,” says Nicholl. “We’ve seen really bright supernovae before and we’ve seen supernovae that fade really quickly, and we’ve seen supernovae in old galaxies, but never all three at the same time.”
The age of Adam’s host galaxy means that it doesn’t have the large, young stars that tend to go supernova. The fact that Adam is located far from its galaxy’s centre rules out the idea that it was caused by a process to do with the galaxy’s central supermassive black hole. Two stars smashing together wouldn’t get so bright.
The remaining explanation is that Adam was caused by a rare intermediate-mass black hole shredding and devouring a star. The process of the star ripping apart would cause the brightening, and intermediate-mass black holes are expected to be fast eaters, which could explain the speedy dimming.
“That’s the hardest one to rule out, so it’s really the biggest option left standing now,” says Nicholl. But the observations aren’t a perfect match – a star being shredded like that should create X-rays, but Adam created very few. The task of explaining Adam’s bizarre lack of X-rays remains an obstacle to understanding the explosion.