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HD 19445

January 19, 2010

Aries, the ram, charges across the western sky on January evenings. He's high in the sky at nightfall.

One of the ram's most important stars is too faint to see without a telescope. Yet half a century ago, it played a key role in a revolutionary discovery: Most of the chemical elements on Earth -- and in our bodies -- were forged in the stars.

A hundred years ago, scientists didn't know where the oxygen, silicon, iron, and other heavy elements that make up Earth came from. A faint star in Aries, named HD 19445, along with another star in Libra, helped point the way.

In 1951, astronomers reported that these two stars had much less iron and calcium than the Sun. It was a shocking report, because most astronomers thought that nearly all stars had the same composition.

Around this time, though, astronomers realized that the two iron-deficient stars were very old, so they'd formed in the galaxy's earliest years. Since the stars had little iron, it meant that the young galaxy itself had little iron. The galaxy has grown more iron-rich over time, though, as stars created iron and spewed it into space. So younger stars like the Sun have higher concentrations of iron and other heavy elements than older stars.

The implication of this discovery was simple but profound: The stars created the iron in our blood, the calcium in our bones, and the oxygen we breathe. We are all children of the stars.

More about another stellar offspring tomorrow.

Script by Ken Croswell, Copyright 2009

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