NASA Hubble Space Telescope Spots Hidden Companion Star to Rare Supernova

NASA's Hubble Space Telescope has caught a glimpse of a companion star to a rare type of supernova. This latest finding confirms the theory that the massive explosion that created the supernova originated in a double-star system, where one star fueled the mass loss from the other star.

"A binary system is likely required to lose the majority of the primary star's hydrogen envelope prior to the explosion," said Ori Fox, lead researcher, in a news release. "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."

While a supernova explodes once every second somewhere in the universe, scientists still don't fully understand what triggers them to explode. Now that they've found a "smoking gun" in the form of a companion star, though, scientists are making headway when it comes to understanding how these star explosions occur.

The supernova is located in the galaxy M81, which is about 11 million light-years away from Earth in the direction of the constellation Ursa Major. Light from this supernova was first detected in 1993 and called SN 1993J. A Type IIb supernova, the explosion has long been thought to have a companion but until now, it's remained hidden.

Now scientists may have just found it. In fact, the companion star is so hot that the so-called continuum glow is largely in ultraviolet light, which can only be detected above Earth's atmosphere. It's likely that this companion star stole a bunch of the primary star's hydrogen before it eventually exploded.

"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," said Alexa Filippenko, one of the team members. "The new Hubble data suggest that we have finally done so, confirming the leading model for Type IIb supernovae."

The findings are published in The Astrophysical Journal.