Scientists Report New Kind 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 death blast of a massive star, they said.
Scores of satellites and ground-based telescopes also are now trained on the sight, researchers said. They added that amateur astronomers in the northern hemisphere with a good telescope in dark skies also can view the source.
The explosion has the trappings of a gamma-ray burst, the most distant and powerful type of explosion known, researchers said.
The collapsing star scenario that is one of the leading contenders as the cause of gamma-ray bursts. See video. Dr. Stan Woosley of the University of California at Santa Cruz proposed the collapsar theory in 1993. This artist's concept of the collapsar model shows the center of a dying star collapsing minutes before the star implodes and emits a gamma-ray burst that is seen across the universe. (Credit: NASA/Dana Berry)
“The observations indicate that this is an incredibly rare glimpse of an initial gamma-ray burst at the beginning of a supernova,” said Peter Brown, a graduate student of Penn State University in University Park, Penn., and 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.
“This is extremely exciting, not only for what it can potentially tell us about the relationship between gamma-ray bursts and ‘ordinary’ supernova explosions, but also because 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.”
In a separate event that further heightened hopes for capturing supernovae early, a European team led by Italy’s National Institute for Astrophysics reported Feb. 24 that it has found hints of a budding supernova.
Scientists are studying a strange explosion that appeared on February 18, 2006, about 440 million light years away in the constellation Aries. The "before" image on the left is from the Sloan Digital Sky Survey. The "after" image on the right is from NASA Swift's Ultraviolet/Optical Telescope. The pinpoint of light from this star explosion outshines the entire host galaxy. Most other sources are foreground stars. Each image is 5 arcminutes by 5 arcminutes (an arcminute equals 1/60 of a degree). Coordinates for this burst, which amateur astronomers can use to train their telescopes, are as follows: RA: 03:21:39.71 Dec: +16:52:02.6. Amateur astronomers in dark skies might be able to see the explosion with a 16-inch telescope as it hits 16th-magnitude brightness, scientists said. (Credits: SDSS [top], NASA/ Swift/ UVOT [bottom].)
The team studied the spectrum of light emitted by the event, using the European Southern Observatory’s Very Large Telescope in Chile.
“We expected to see the typical featureless spectrum of a gamma-ray burst afterglow, but instead we found a mixture between this and the more complex spectrum of a supernova similar to those generally observed weeks after the gamma-ray burst,” said Nicola Masetti of the institute. “A supernova must be in the works.”
- Courtesy Penn State University
and World Science staff