La supernova SN 2017 egm was discovered on 23 May 2017 by astronomers at the University of Cambridge. It is located in a spiral galaxy about 420 million light years away and has a high concentration of elements heavier than hydrogen and helium. It is the first evidence of a metal-rich birthplace for a superluminous supernova, which is why it’s been nicknamed the ‘heavy metal’ supernova.