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Supernova Turned Star Inside-Out

When the star Cassiopeia A exploded, nearly all the iron from the core was expelled to the outer regions of the supernova. John Matson reports

It’s a blast from the not-too-distant past.

Cassiopeia A is a giant, expanding shell of debris about 11,000 light-years away. It’s one of the youngest remnants of a supernova, an exploded star, in our galaxy. The light from the explosion first reached eyes on Earth around 1670.

But only with the advent of modern telescopes has the supernova’s nature really come to light. Because a few years ago astronomers concluded that the explosion followed the collapse of a massive star. Now an accounting of the material cast outward in the supernova is giving astrophysicists clues to the explosion itself.

Researchers used one million seconds of observing time on the orbiting Chandra X-Ray Observatory to carefully scan the supernova remnant. That’s more than 11 days on one of NASA’s premier telescopes. What they found, among other things, was that the ejecta from the supernova has not spread outward evenly.

Instead, nearly all the iron from the core of the star has been expelled to the outer regions of the supernova remnant. The supernova essentially turned the star inside out. [Una Hwang and J. Martin Laming, "A Chandra X-Ray Survey Of Ejecta In The Cassiopeia A Supernova Remnant" in The Astrophysical Journal]

Think about that—and be glad your ancestors were 11,000 light-years away when it happened.

—John Matson

[The above text is a transcript of this podcast.]

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