After 20 years of search, astronomers with the help NASA's Hubble Space Telescope have found a companion star of supernova in close orbit. The discovery confirms a long-held belief that supernova SN 1993J happened inside a binary system. It is a system, where two stars interact with each other and cause a cosmic explosion.

SN 1993J was an example of a Type IIb supernova. Type IIb's have much less hydrogen than found in a typical supernova. According to astronomers, the companion star took most of the hydrogen from the exploding main star and continued to be 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", said lead researcher Ori Fox of UC Berkeley.

Since the time, SN 1993J was discovered, the search for the companion star was going on. According to astronomers at Hawaii's Keck Observatory, the companion star released great amount of ultraviolet light, but scientists were not sure that whether or not they had found the accurate star to measure.

With the help of optical light data and Hubble's UV light photos, the team made a spectrum that matched the forecasted glow of a companion star. Recently, scientists have been able to identify this glow as the continuum emission.

Azalee Bostroem of the Space Telescope Science Institute (STScI) said that the Hubble helped them to have the UV spectrum. It shows that there is surplus of continuum emission in the UV, even when the light from other stars has been taken away.

The new data will surely prove beneficial for astronomers interested in different mechanisms of supernova. It was estimated that a supernova takes place every second somewhere in the universe, but astronomers do not have complete knowledge on what causes the explosion.