Using the Hubble Space Telescope, astronomers have discovered a companion star to a rare type of supernova. The discovery confirms a long-held theory that the supernova, dubbed SN 1993J, occurred inside what is called a binary system, where two interacting stars caused a cosmic explosion.
SN 1993J is an example of a Type IIb supernova, unusual stellar explosions that contains much less hydrogen than found in a typical supernova. Astronomers believe the companion star took most of the hydrogen surrounding the exploding main star and continued to burn as a super-hot helium star.
SN 1993J resides in the Messier 81 galaxy, about 11 million light-years away in the direction of Ursa Major, the Great Bear constellation. Since its discovery 21 years ago, scientists have been looking for the companion star. Observations at the W. M. Keck Observatory on Mauna Kea, Hawaii, suggested that the missing companion star radiated large amounts of ultraviolet (UV) light, but the area of the supernova was so crowded that scientists could not be sure they were measuring the right star.
The team combined optical light data and Hubble’s UV light images to construct a spectrum that matched the predicted glow of a companion star, also known as the continuum emission. Scientists were only recently able to directly detect this light.
Pictured here is an artist’s impression of supernova 1993J, which exploded in the galaxy M81.
Image Credit: NASA, ESA, G. Bacon (STScI)