 January 11, 2007—The most detailed x-ray image yet of one
of the youngest known supernova remnants—the debris cloud
created when a massive star explodes—solves a long-standing
mystery about how the star died, an astronomer announced on Tuesday.
About 400 years ago people on Earth, including the famous German astronomer Johannes Kepler, saw the light from a supernova.
The explosion was so bright that it was visible with the naked eye even though it occurred about 13,000 light-years away.
Scientists have been studying what became known as the Kepler supernova
remnant for about 30 years, but the formation had left them baffled
about the type of explosion that created it.
So far, scientists know of two types of supernovas: core-collapse and thermonuclear.
Previous images suggested that the Kepler remnant is surrounded
by dense material, as expected from a core collapse. But the formation
also appeared to contain copious amounts of iron, a signature of a
thermonuclear explosion.
The new image, made with NASA's Chandra X-ray Observatory,
clearly shows abundant iron (yellow) and sparse oxygen, proving the
Kepler blast was thermonuclear, said Stephen Reynolds of North Carolina
State University in Raleigh.
"But at the same time we confirmed the presence of
circumstellar material [red]," which is normally a telltale sign of
core collapse, Reynolds said. The finding could mean that Kepler
belongs to a new class of thermonuclear supernova, he added.
But for now, Reynolds said, the image just shows that "it has both [features]. … Live with it. That's Chandra's message."
—John Roach
http://news.nationalgeographic.com/news/2007/01/070111-supernova.html
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