Hubble Finds Supernova Companion Star after Two Decades of Searching

This is an artist's impression of supernova 1993J, an exploding star in the galaxy M81 whose light reached us 21 years ago. The supernova originated in a double-star system where one member was a massive star that exploded after siphoning most of its hydrogen envelope to its companion star. After two decades, astronomers have at last identified the blue helium-burning companion star, seen at the center of the expanding nebula of debris from the supernova. The Hubble Space Telescope identified the ultraviolet glow of the surviving companion embedded in the fading glow of the supernova.

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Using NASA’s 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.

"This is like a crime scene, and we finally identified the robber," said Alex Filippenko, professor of astronomy at University of California (UC) at Berkeley. "The companion star stole a bunch of hydrogen before the primary star exploded."
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.

“A binary system is likely required to lose the majority of the primary star’s hydrogen envelope prior to the explosion. The problem is that, to date, direct observations of the predicted binary companion star have been difficult to obtain since it is so faint relative to the supernova itself,” said lead researcher Ori Fox of UC Berkeley.

Read more: 1.usa.gov/1Az5Qb9

Credit: NASA, ESA, G. Bacon (STScI)

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