How to catch a supernova explosion before it happens – and what we can learn from it

Stars are born, live and die in spectacular ways, with their deaths marked by one of the biggest known explosions in the Universe. In 2009, astronomers observed a bright event 65 million light years away that on first impressions resembled a supernova explosion. Dubbed SN 2009ip, the explosion did not brighten as expected and was reclassified shortly after discovery as a “supernova impostor” – a giant eruption which ultimately does not destroy the star. The star was observed very slowly increasing its brightness for over five years – akin to slowly turning on a bulb using a dimmer switch – before a supernova was observed. For example, in the 1840s, Eta Carinae – a star 100 times larger than the Sun – experienced the “Great Eruption” launching 30 times the Sun’s mass into space.