Rare supernova 'impostor' found in nearby galaxy

A team of astronomers has found a rare supernova "impostor" in a nearby galaxy.

University of Washington's Breanna Binder and her colleagues recently solved a mystery involving X-rays-a case of X-rays present when they shouldn't have been. This mystery's unusual main character, a star that is pretending to be a supernova, illustrates the importance of being in the right place at the right time.

Such was the case in May 2010 when an amateur South African astronomer pointed his telescope toward NGC300, a nearby galaxy. He discovered what appeared to be a supernova, a massive star ending its life in a blaze of glory.

After a star explodes as a supernova, it usually leaves behind either a black hole or what's called a neutron star, the collapsed, high-density core of the former star. Neither should be visible to Earth after a few weeks. But this supernova, SN 2010da, still was.

SN 2010da is what they call a 'supernova impostor,' something initially thought to be a supernova based on a bright emission of light, but later to be shown as a massive star that for some reason is showing this enormous flare of activity, said Binder.

Many supernova impostors appear to be massive stars in a binary system, two stars in orbit of one another. Stellar astrophysicists think that the impostor's occasional flare-ups might be due to perturbations from its neighbor.

For SN 2010da, the story appeared to be over until September 2010, when Binder found that there was just this massive amount of X-rays coming from SN 2010da, which "you should not see coming from a supernova impostor."

The study appears in the Monthly Notices of the Royal Astronomical Society.