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Moon and Spica

February 3, 2010

As the Moon climbs into view around midnight, a bright star shines just a little to its upper left: Spica, the leading light of the constellation Virgo. They'll stand low in the sky at first light tomorrow, with Spica to the upper right of the Moon.

Like all the stars that blaze through the night, Spica is a stellar recycling center. Its two main stars -- each of which is bigger and heavier than the Sun -- were born just a few million years ago, from a giant cloud of gas and dust. Some of the material in the cloud had been blown into space from other stars.

The cloud that gave birth to Spica covered a large volume of space. But something caused it to collapse -- like the shockwave from an exploding star. As the cloud collapsed, it split apart. The smaller clouds continued to collapse, getting hotter and hotter at their centers. When they got hot enough, nuclear fusion was ignited, and the stars of Spica were born.

These stars are heavy, so they're manufacturing a variety of elements. Eventually, the list may include iron. Fusion will stop then, and the stars may explode, scattering the elements they created into space. And the explosions themselves will forge even more elements.

This material will scatter through space, where it can be incorporated into other clouds. Some of these clouds may collapse and give birth to stars, too -- triggered by the explosions of stars like Spica -- nature's cosmic recycling centers.

Script by Damond Benningfield, Copyright 2009

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