March 26, 2013
Astronomers Identify New Type Of Supernova 100 Times More Massive Than Our Sun
Lee Rannals for redOrbit.com — Your Universe Online
Astronomers discovered a new type of supernova of a star about 10 to 100 times more massive than our sun.
The Type Iax supernova is a fainter and less energetic explosion than the Type Ia, and may not completely destroy the white dwarf star; type Ia supernovae completely destroy their tiny white dwarfs.
"A Type Iax supernova is essentially a mini supernova," says lead author Ryan Foley, Clay Fellow at the Harvard-Smithsonian Center for Astrophysics (CfA). "It's the runt of the supernova litter."
Astronomers writing in The Astrophysical Journal said they identified 25 examples of the new supernova, none of which appeared in elliptical galaxies. These types of galaxies are filled with old stars, so the lack of a Type Iax supernova sitting in this galaxy suggests these explosions come from young star systems.
The team found that a Type Iax comes from a binary star system containing a white dwarf and a companion star that has lost its outer hydrogen, leaving it full of helium. The white dwarf collects helium from the normal star, and the astronomers theorize that the outer layer of the gas ignites first, sending a shockwave into the white dwarf. They also say the white dwarf might ignite first due to the influence of the overlying helium shell.
According to the research, in many cases the white dwarf survives the explosion, unlike a Type Ia explosion.
"The star will be battered and bruised, but it might live to see another day," says Foley.
He says the Type Iax supernovae are about a third as common as Type Ia supernovae, but the reason few have been spotted until now is because they are only one-hundredth as bright as a Type Ia.
"Type Iax supernovas aren't rare, they're just faint," said Foley. "For more than a thousand years, humans have been observing supernovas. This whole time, this new class has been hiding in the shadows."
NASA's Swift space observatory recently discovered the remains of the youngest known supernova at just 2,500 years old. Lead scientist Mark T. Reynolds, a postdoctoral researcher at the University of Michigan said it was one of the 20 youngest remnants ever identified.
Scientists believe supernovae only occur once or twice per century in our Milky Way galaxy. Astronomers have cataloged over 300 supernova remnants in our galaxy. Scientists determine the age of a supernova after considering the distance and the speed at which the explosion's shockwave races towards Earth.
One of the rarest known classes of a supernova is a Type Ibn. Only five previous events have ever been seen of this type of supernova, and they were all found in galaxies similar to our own. Astronomers believe these types of supernovae are the result of the collapse of massive stars that ejected massive amounts of helium prior to their collapse.
The Large Synoptic Survey Telescope (LSST) could help astronomers discover thousands of Type Iax supernovas.