Study Discovers Likely Source of Rare Supernova Explosion

A new paper published in the latest issue of Astrophysical Journal Letters outlines the discovery of a Type Ib supernova, or a rare explosions of a star without an outer layer of hydrogen -- the most abundant element in the universe. The study, led by researchers from the California Institute of Technology (Caltech), offers the first direct evidence of the kind of star behind the explosion.

Researchers have long struggled to determine the kind of star that produces a Type Ib supernova. According to Yi Cao, a graduate student at Caltech and lead author of the study, one of the most likely sources are Wolf-Rayet stars. Ten times more massive and thousands of times brighter than the Sun, Wolf-Rayet stars are objects that have lost their hydrogen envelope in the onslaught of furious stellar winds.

For years, however, no direct evidence supporting this theory could be identified. Now, Cao and his colleagues say they have found a young supernova at a site previously home to a likely Wolf-Rayet star.

Using an adaptive optics system to reduce the blurring effects of the Earth's atmosphere, the team obtained a high-resolution image of the supernova and then compared it to a series of images of the same galaxy taken by the Hubble Space Telescope in 2005.

In doing so, they identified a starlike object in the earlier images located in the same region as the supernova. The star, further analysis revealed, exhibited the brightness, color, size and history of mass loss indicative of a Wolf-Rayet star.

"All evidence is consistent with the theoretical expectation that the progenitor of this Type Ib supernova is a Wolf-Rayet star," Cao said.

Going forward, the researcher said, "Our next step is to check for the disappearance of this progenitor star after the supernova fades away. We expect that it will have been destroyed in the supernova explosion."