Newly Discovered Companion Star Hidden in Supernova's Glare for 21 Years

NASA's Hubble Space Telescope just recently discovered a companion star after being hidden for 21 years in the glare of a rare type of supernova, according to new research.

The exploding supernova in question, dubbed SN 1993J, was first detected in 1993, and is the only known example of a rare Type IIb supernova - which have a minimal amount of hydrogen present. Astronomers theorized that the supernova originated in a double-star system, and have since been searching for its suspected companion, thought to be lost in the glare of the residual glow from the explosion.

"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," lead researcher Ori Fox of the University of California (UC) at Berkeley said in a news release.

Supernovae supposedly go off once every second somewhere in the Universe, and yet the mechanism behind these explosions is still largely unknown. However, finding a companion star could provide new clues to these mysterious phenomena.

"This is like a crime scene, and we finally identified the robber," explained Alex Filippenko, professor of astronomy at UC Berkeley.

Located 11 million light-years away in the galaxy M81, the companion star's glow can only be detected in ultraviolet light - and Hubble did just that. By observing continued UV light after subtracting the light emitted from other stars, Hubble conclusively proved the existence of SN 1993J's companion star.

"When I first identified SN 1993J as a Type IIb supernova, I hoped that we would someday be able to detect its suspected companion star," Filippenko said. "The new Hubble data suggest that we have finally done so, confirming the leading model for Type IIb supernovae."

The findings were published in The Astrophysical Journal.