Astrophysicists from the University of Tokyo have affirmed the standard theory that only red supergiants and Wolf-Rayet or blue stars can become supernovae.

The model was called into question when the yellow supergiant star went supernova, apparently by itself. This supernova, SN 2011dh, occurred in the whirlpool galaxy M51 located 24 million light years away from Earth.

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A team from the Kavli IPMU at the University of Tokyo led by Gastón Folatelli had previously predicted the existence of a companion star on the basis of numerical calculations. That no companion star was apparent at the birth of SN 2011dh prompted the team to begin an intensive search for the companion star.

The team eventually found evidence of a bright blue star, the binary companion star to SN 2011dh using the Hubble Space Telescope.

This finding has wide-ranging implications for our knowledge of binary systems and supernova mechanisms. It seems t confirm that most massive stars belong to close binary systems.

Episodes of mass transfer between the members of binary star systems affect the way the stars evolve, meaning that there are many more potential scenarios for the final stages of supernova ancestors.

Supernova SN 2011dh seemed to be the exception because the standard theory couldn't explain it. The star that gave birth to this supernova was a yellow supergiant star.

Astronomers know supergiant stars in isolation aren't thought capable of becoming supernovae.

What the Kavli IPMU team showed was that the exploding yellow star must have been extended (like a yellow supergiant) and must have belonged to a binary system.

"We produced detailed models that self-consistently explained every property of SN 2011dh through the explosion of a yellow supergiant star in a binary system," said Melina Bersten to Phys.org.

The standard theory states only cool and extended stars (or red supergiants) or hot and blue stars (better known as Wolf-Rayet stars) are able to become supernovae.