Scientists theorized that supernova Ia explosions are triggered by the sudden fusion of carbon and oxygen into heavier elements, such as nickel-56, inside a white dwarf star, making it unstable.
"Fusion happens in a flash," astrophysicist Robert Kirshner, with the Harvard-Smithsonian Center for Astrophysics, writes in an article in this week's Nature. "A thermonuclear flame rips through the white dwarf, fusing carbon into heavier elements with a sudden release of energy that tears the star apart. Fusion stops yielding energy at the element that has the most tightly bound nucleus - in the case of a white dwarf, nickel-56."
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When the exploded remains of the M82 star were found, astronomers moved quickly to find out if the theoretical predictions were right.
"The last type Ia in our galaxy was in 1604," lead researcher Eugene Churazov, with Germany's Max Planck Institute for Astrophysics, wrote in an email to Discovery News.
He and colleagues used the European Space Agency's International Gamma-Ray Astrophysics Laboratory, nicknamed INTEGRAL, to observe the newly found supernova between 50 and 100 days after the explosion. They found a neat chain of chemistry caused by the decay of radioactive nickel isotopes into cobalt and iron. Calculations show the amount of radioactive nickel, the rate of the supernova expansion and the amount of mass produced in the explosion match predictions.