Astronomers say they have detected a new type of cosmic explosion.
Radiation from the blast, detected on Feb. 18 and lasting about
half an hour, appears to be a precursor to a supernova.
The explosion has the trappings of a gamma-ray burst,
the most distant and powerful type of explosion known.
"The observations indicate that this is an incredibly rare glimpse
of an initial gamma-ray burst at the beginning of a supernova,"
said a member of the Swift science team.
This event, however, was about 25 times closer and 100 times
longer than the typical gamma-ray burst, the researchers added.
It was "totally new and unexpected," said Neil Gehrels, principal
investigator for NASA's Swift satellite, which was used to make the
finding. "This is the type of unscripted event in our nearby universe
that we hoped Swift could catch."
The explosion, called GRB 060218 after the date it was discovered,
originated in a star-forming galaxy about 440 million light-years away
toward the constellation Aries. This is the second closest gamma-ray
burst ever detected, if indeed it is a true burst, researchers said.
"The detection of the gamma-ray flash has alerted us to the
potential presence of a nearby supernova, which we can now study
in detail from the very beginning," said Keith Mason, chief executive
of the U.K.'s Particle Physics and Astronomy Research Council, one of
the researchers.
"Usually these events are not detected until after the exploding
star has brightened substantially."