Stellar Tease

A giant star that teased astronomers into thinking it had exploded three years ago finally blasted itself to bits last year.

When the star produced a mammoth eruption in 2009, astronomers designated it as Supernova 2009ip. Within days, though, they had second thoughts. The explosion faded too quickly for a true supernova, and the material it blasted into space was moving too slowly. Astronomers realized the star had duped them.

After a similar outburst a year later, 2009ip staged a third eruption last July. It remained bright for weeks, and the ejected material was traveling at a few percent of the speed of light. In other words, this outburst really was a supernova.

Pictures snapped over a period of about 10 years before the final explosion revealed that the star was a luminous blue variable. Such stars are dozens of times as massive as the Sun and a million times brighter. 2009ip is the first confirmed instance of such a star exploding as a supernova.

Astronomers aren’t sure what