The companion star's image, seen in the fading afterglow of a supernova that exploded about 40 million light-years across the galaxy NGC 7424, provides the most compelling evidence that some supernovae come from binary star systems. According to the study, the companion star of the Supernova was not just an innocent observer of the explosion. Instead, it was probably the instigator.
The supernova in question, SN 2001
Originally, astronomers believed that the precursor stars of these supernovae lost their outer shells due to the incredibly strong and fast stellar winds. However, this theory seems incomplete, as the observers have not found enough precursor stars to make it the only possible scenario. "This was particularly bizarre because astronomers expected them to be the most massive and bright progenitor stars," said co-author Ori Fox, an astronomer at the Space Telescope Science Institute in Baltimore, in a press release. "Moreover, the sheer number of stripped-coat supernovae is larger than predicted."
This discrepancy between prediction and observation prompted astronomers to postulate that splintered-envelope type IIb supernovae could instead be a result of binary pairs. "We know that most massive stars are binary pairs," said lead author Stuart Ryder, an astronomer at the Australian Astronomical Observatory (AAO) in Sydney. "Many of these binary pairs will interact and transmit gas from one star to another as their orbits bring them close together."
In the case of SN 2001ig, it is assumed that the companion star has evacuated almost all of the hydrogen from the outer shell of the precursor of the supernova. Since the outer region of a star is extremely efficient at transmitting energy from the nucleus to the outside, the absence of a shell can have dramatic effects. Especially in the course of millions of years, the companion star robbed so much material from the shell of the primary star that it created instability. This eventually led to the precursor star having to eject massive hydrogen gas casings at regular intervals to trigger an epic explosion.