The force of an exploding star may have ripped material off an orbiting companion star, leaving behind a signature glow.

Astronomers first spotted the massive explosion of supernova iPTF13ehe in 2013. Two years later, they noticed an afterglow coming from clouds of hydrogen nearby. Takashi Moriya at the University of Bonn in Germany and his colleagues argue that this unexpected light came from material that was torn off another star during the violent original outburst. The energy from the blast could have blown away part of a tightly orbiting companion star, stripping off a mass of hydrogen that could weigh nearly as much as the Sun.

Careful scrutiny of hydrogen emissions from other especially bright supernovae could determine whether this radiance stems from companion stars or matter that is already present in the surrounding interstellar space.

Astron. Astrophys. 584, L5 (2015)