for National Geographic News
Two small but dense burned-out stars appear to have spiraled into each other and exploded, according to a new study.
The blast offers some of the strongest evidence yet for a theoretical model for supernovas created by white dwarfs—the hot cores left behind when stars similar to our sun die.
The finding could also have implications for studies of dark energy, a mysterious force thought to make up more than 70 percent of the universe.
Most white dwarf supernovas are believed to occur when the tiny dead stars siphon so much material from a larger, nearby star that they trigger a massive fusion reaction and explode.
The leading theory is that matter is being siphoned from a red giant—a type of star that is dying but not yet completely burned out.
The same explosion could also occur, however, if two white dwarfs merged, said Malcolm Hicken, an astrophysicist at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts.
Hicken and his colleagues now conclude that such a merger best explains the unusual properties of an extraordinarily bright supernova observed last year dubbed 2006gz.
The team's findings are described in the November 1 issue of the Astrophysical Journal Letters.
Current models classify supernovas as either Type I or Type II, the major difference being that only Type II blasts show evidence of hydrogen.
Astronomers had initially characterized supernova 2006gz—spotted 300 million light-years away in the constellation Hercules—as a Type Ia because it lacked hydrogen.
(See a picture of an unusual Type Ia supernova spotted on March 1, 2007.)
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