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Astronomers Glimpse Supernova Shockwave

Astronomers have captured the earliest minutes of two exploding stars, and for the first time seen a shockwave generated by a star’s collapsing core. “It’s like the shockwave from a nuclear bomb, only much bigger and no one gets hurt,” said Dr Brad Tucker of The Australian National University.

Stars explode when their fuel runs down and the core collapses. The resulting supernova explosion is brighter than the rest of its galaxy, and shines for some weeks.

Supernovae are so bright that they can be seen in distant galaxies, but very little is known about the early stages of these explosions.

As the core of a supernova collapses to form a neutron star, energy bounces back from the core in the form of a shockwave that travels at 30–40,000 km/s and causes the nuclear fusion that creates heavy elements such as gold, silver and uranium.

The new study, published in the Astrophysical Journal (http://tinyurl.com/zfplud3), reports the explosions of two red supergiants. The astronomers only saw a shockwave in the smaller star, which has a radius 270 times that of the Sun. The shockwave was observed as a peak in the light emitted from the explosion in the first few days.

While a shockwave could not be detected in the second star, a large supergiant with a radius 460 times larger than the Sun, Tucker said that it must have existed. “The star was so large that the shockwave did not travel all the way to the surface,” he explained.

The observation will help astronomers fine-tune their understanding of how the size and composition of a star affects the early moments of its death. “Supernovae made the heavy elements we need to survive, such as iron, zinc and iodine, so we are really learning about how we are created,” Tucker said.