Astronomers have discovered a new class of supernova, according to a news release from the Carnegie Institution for Science. Prior to this study, supernovae were separated into either core-collapse or Type Ia categories. Now, astronomers have found a new type of supernova called Type Iax.
The first kind of supernova (core-collapse) is the explosion of a star approximately 10 to 100 times as massive as our sun. In a Type Ia supernova, the star “becomes unstable and essentially the entire star is consumed in a gigantic thermonuclear explosion,” according to the University of Tennessee at Knoxville.
A Type Iax supernova is a lot less “energetic” than Type Ia. While both types of supernovae originate from exploding white dwarfs, Type Iax supernovae may not entirely annihilate the white dwarf.
According to lead author Ryan Foley, Clay Fellow at the Harvard-Smithsonian Center for Astrophysics, a Type Iax supernova is “the runt of the supernova litter.”
The astronomers found 25 examples of Type Iax supernovae. They believe that Type Iax supernovae come from young star systems because none of the examples were located in elliptical galaxies, which typically contain old stars.
The astronomers reached the conclusion that a Type Iax supernova originates from a binary star system holding a white dwarf and a companion star that has lost its outer hydrogen, allowing helium to reign supreme. The white dwarf gathers helium from its companion star.
A Type Iax supernova may be brought about by the ignition of the companion star’s outer helium later, which emits a shock wave that impacts the white dwarf. In another plausible scenario, the white dwarf might explode first given the influence of the overlying helium shell. Astronomers believe that the white dwarf makes it through the explosion in a Type Iax supernova, whereas a Type Ia supernova completely destroys the star.
Astronomers think that Type Iax supernovae are approximately a third as common as Type Ia supernovae.
“The closer we look, the more ways we find for stars to explode,” Carnegie’s Mark Phillips said.
The study’s findings will appear in The Astrophysical Journal.