Steady Star

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The outer layers of the Sun are pretty mixed up. Big bubbles of hot gas boil to the surface like a pot of tea. And the Sun turns on its axis about once a month, stirring things up even more.

But some stars have much less turbulent outer layers. This may let astronomers see a whole periodic table of heavy elements that are rarely seen in stars like the Sun.

An example is one of the stars in the multiple-star system Beta Capricornii. It's in Capricornus, the sea-goat, which slides across the southern sky on autumn evenings.

It's described as a "mercury-manganese" star. That means that when astronomers split the star's light into its individual colors, they see the chemical fingerprint of lots of these elements.

In the case of the lesser star of Beta Capricornii, they also see lots of gold and platinum -- around a hundred thousand times more of these elements than they see in the Sun.

But the stars may not really have that much more of the elements than the Sun does. Instead, the outer layers of these stars are much steadier than the Sun. The stars rotate slowly, and they don't have the same "boiling" action at the surface. That may allow radiation and gravity to separate the chemical elements and push some of them to the surface.

Beta Capricornii and similar stars are heavier than the Sun, and they're farther along in their life cycles. The difference helps keep their outer layers steady -- revealing more of their chemical makeup.

Script by Damond Benningfield, Copyright 2008

For more skywatching tips, astronomy news, and much more, read StarDate magazine.