A supernova is the only event in existence that happens on both astronomical and human scales (If you think of others – tell me). It involves a massive stellar explosion and release of energy that can match the output of an entire galaxy, yet this release happens in the blink of a cosmic eye, about two weeks. For all that could live in the incredibly vast amounts of empty space between galaxies, a supernova is a great indicator that stars do in fact inhabit this space. Recently, the Hubble Space Telescope confirmed that two such supernovae have been discovered.
In 2009, the Canada-France-Hawaii Telescope (CFHT) discovered two distant supernovae that appeared to have no associated home galaxy. Recently, observations by Hubble have confirmed that the rogue supernova do not in fact belong to any galaxy, that they are truly the explosions of ejected stars.
“They belong to a population of solitary stars that exist in most if not all clusters of galaxies,” said Dr Melissa Graham from the University of California, Berkeley. “Any planets around these intracluster stars were no doubt obliterated by the explosions, but they would have had a night sky depleted of bright stars. The density of intracluster stars is about one-millionth what we see from Earth,”
Members of massive galaxy clusters, due to their large gravitational tidal forces, are thought to lose about 15% of their stars to intergalactic space over their lifetime. We would never directly observe them if not for supernova explosions. Imagine living on a planet around such a star. As lonely as humanity feels on Earth with the stars so distant yet seemingly so close, a species on an intergalactic interloper star system would truly be lost in the dark.