Supernova 1993J

This image shows the supernova 1993J which is situated inside the majestic spiral galaxy M81. It can be seen in situ in the annotated image.

Though astronomers saw the star explode as a supernova 21 years ago, the glow of that explosion is still present, as seen here. The supernova has faded to the point where astronomers are confident that they have picked up the ultraviolet glow of a very hot companion star. This is the first time astronomers have been able to put constraints on the properties of the companion star in this unusual class of supernova called Type IIb. Hubble observations in ultraviolet light confirm the theory that the explosion originated in a double-star system where one star fueled the mass-loss from the aging primary star.