Astronomers canvassing the sky for asteroids that could threaten Earth stumbled upon a supernova in a galaxy 650 million light-years away, Jet Propulsion Laboratory announced Friday.
The supernova was photographed by NASA's Near Earth Asteroid Tracking system on Feb. 18. The images captured the star's appearance just a few weeks after the ancient explosion occurred.
The discovery was a bonus for astronomy, said Steven Pravdo, project manager and co-investigator for NEAT.
"We were fishing for salmon, and instead we caught a whale," Pravdo said in a statement released by JPL.
The star was unknown to astronomers prior to the accidental discovery.
The supernova, named 1999am, was a white dwarf star in orbit with a companion star before it exploded. The white dwarf captured so much material from the companion that it became too massive to support itself.
The explosion had as much energy as 100 billion suns, and the supernova is now nearly as bright as the surrounding galaxy, JPL said.
The JPL-managed NEAT project has been operating since 1995, using an automated camera mounted on a telescope operated by the Air Force atop Mount Haleakala on Maui in the Hawaiian islands.
Pravdo said the Feb. 18 observation data was sent to Lawrence Berkeley National Laboratory in Berkeley, Calif., where Greg Aldering and other scientists with the Supernova Cosmology Project quickly spotted 1999am.
The Berkeley scientists compared the February images with other NEAT data and spotted a change in brightness, indicating the star had exploded. They also used other telescopes to confirm the finding.
NEAT tries to detect potentially hazardous objects approaching Earth by looking for celestial bodies that move over a period of time. The data also can be used to search for stationary objects that grow brighter or dimmer as time passes.
The supernova, at a distance of 650 million light years, is harmless. A light year is the distance light travels in one year, about six trillion miles.
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