WASHINGTON -- In what amounts to a cosmic train wreck, astronomers for the first time are seeing the effects of an enormous shock wave from an exploded star as it crashes into the star's outermost remains.
"In any large explosion, you get a flash of light followed by a shock wave," said David Burrows, a Penn State physicist who studied the blast with NASA's
The light from that explosion -- 30 million times as bright as our sun -- was first detected from Earth in 1987. It was the brightest supernova that astronomers had seen in 400 years.
Recent observations from the Hubble Space Telescope showed gradually brightening hot spots from a spherical shell of dense gas that had been ejected by the star about 20,000 years before the star exploded.
Chandra's X-ray images show the reason for that brightening. A shock wave traveling 30 million m.p.h. (48.3 million kilometers per hour) is smashing into the shell, heating it to 54 million degrees Fahrenheit (30 million degrees Celsius). The gas is visible only with an X-ray telescope.
The gaseous shell around Supernova 1987-A is about a light-year in diameter -- about 6 trillion miles (9.65 trillion kilometers) -- and measures about a tenth of a light-year thick.
"A supernova takes place about once a century so you only get one per lifetime."
The shock wave is expected to pass through the shell, blowing it to bits. But those gas bits are expected to glow 100 or 1,000 times brighter than they are now for as long as a decade.
Even after that, astronomers expect the gas remnants will glow in X-rays for perhaps a thousand years.
As for the shock wave, "it will keep on going far beyond the shell and it might even lead to the formation of new stars," said Robert Kirshner, an astronomer at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts.
Scientists are especially excited to watch the supernova evolve because exploding stars are a relatively rare event.
"A supernova takes place about once a century so you only get one per lifetime," Kirshner said.
"It's the biggest bang in the universe since the Big Bang, and new atoms are formed out of it," he said. "Every atom in our body, or even the atoms in the chair you're sitting in, come from the remains of these exploded stars."
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