Kepler's supernova remnant. The explosion of a star is a catastrophic event. The blast rips the star apart and unleashes a roughly spherical shock wave that expands outward at more than 35 million kilometers per hour (22 million mph) like an interstellar tsunami. What might happen when a really gargantuan star — one hundreds of times bigger than our sun — blows up? (Credit: NASA)

ScienceDaily (Dec. 4, 2009) — What happens when a really gargantuan star — one hundreds of times bigger than our sun — blows up? Although a theory developed years ago describes what the explosion of such an enormous star should look like, no one had actually observed one — until now.

An international team, led by scientists in Israel, and including researchers from Germany, the US, UK and China, tracked a supernova — an exploding star — for over a year and a half, and found that it neatly fits the predictions for the explosion of a star of over 150 times the sun's mass. Their findings, which could influence our understanding of everything from natural limits on star size to the evolution of the universe, appeared recently in Nature.

'It's all about balance,' says team leader Dr. Avishay Gal-Yam of the Particle Physics and Astrophysics Department. 'During a star's lifetime, there's a balance between the gravity that pulls its material inward and the heat produced in the nuclear reaction at its core, pushing it out. In a supernova we're familiar with, of a star 10 -100 times the size of the sun, the nuclear reaction begins with the fusion of hydrogen into helium, as in our sun. But the fusion keeps going, producing heavier and heavier elements, until the core turns to iron. Since iron doesn't fuse easily, the reaction burns out, and the balance is lost. Gravity takes over and the star collapses inward, throwing off its outer layers in the ensuing shockwaves.'

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