More Cassiopeia A
More than three centuries ago as seen from Earth, a giant star blew itself apart as a supernova. Its remains -- some colorful wisps of gas, along with smatterings of heavy elements created in the explosion -- now form a "bubble" that spans about 10 light-years.
The bubble is a "supernova remnant" known as Cassiopeia A -- Cas A for short.
Our galaxy is littered with supernova remnants. But Cas A is the most interesting, because its explosion took place more recently than any other in the galaxy. That means the expanding remnant is still pretty compact, so astronomers can study its structure to learn about the explosion.
And there's still quite a bit to learn.
For one thing, even though Cas A should have shined brighter than the full Moon in Earth's sky, there's little or no record that anyone saw it. Astronomers want to know if the star puffed most of its outer layers into space before it exploded, surrounding it with a cocoon of gas that blocked it from view.
And Cas A shows evidence that "jets" of material squirted away from the supernova's poles, perhaps helping to power the explosion. But the jets contain less material than astronomers expected to see. And even more intriguing, it shows extra jets. That may mean that the explosion produced extra-powerful magnetic fields, or that something even more exotic was taking place deep inside the star.
Astronomers continue to study Cas A to learn more about its violent demise.
Script by Damond Benningfield, Copyright 2006
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