NASA's Hubble identifies 'rare type' of supernova companion star

NASA's Hubble Space Telescope has recently discovered a companion star to a rare type of supernova in close orbit after two decades of searching. The discovery confirmed a long-held theory that the supernova, dubbed SN 1993J, occurred inside what was called a binary system, where two interacting stars caused a cosmic explosion.

Alex Filippenko, professor of astronomy at University of California (UC) at Berkeley said that the companion star stole a bunch of hydrogen before the primary star exploded. SN 1993J was 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.

Astronomers estimated a supernova occurs once every second somewhere in the universe, yet they don't fully understand how stars explode. Further research would help astronomers better understand the properties of this companion star and the different types of supernovae. The study is published in the Astrophysical Journal.