A Star is Born Nebulae containing molecules show us where stars might form. Here’s why. Space is a harsh place. Starlight destroys molecules. T e only places where molecules can survive are where material is fairly dense. T ere, dust in the cloud shields molecules from the starlight that would tear them apart. So nearly all stars form in what we call molecular clouds. Molecular hydrogen is tough to detect.
Fortunately, there are other molecules in space, like carbon monoxide. T is has one carbon atom and one oxygen atom. Carbon monoxide gas has a bad reputation on Earth. It kills. It’s given off by cars and cigarettes. But in space, carbon monoxide gas shows where stars form. Carbon monoxide molecules give off radio
waves. T ese waves travel at the speed of light but have much longer wavelengths than visible light does. Our eyes can’t see them, but we can build telescopes that detect radio waves. T ese telescopes are called radio telescopes. In this way we can fi nd carbon monoxide in space.
Star Light, Star Bright T e most famous molecular cloud contains the Orion Nebula. You can see the Orion Nebula on a winter’s night if the sky is dark and clear, and there’s no moon. It’s in the constellation Orion. T e Orion Nebula has given birth to thousands of stars.T e Orion Nebula is beautiful. So are many other clouds in space. One of my favorites is the Horsehead Nebula, which looks like the knight in a chess game. T ere are plenty of molecules besides
hydrogen in these clouds. Astronomers have discovered substances such as water and ammonia. T ey have even found “buckyballs.” T ese molecules have 60 carbon atoms. T ey’re shaped like the domes built by the American architect R. Buckminster Fuller, which is why they’re called “buckyballs.” Molecular clouds might have thousands
or even millions of molecules per cubic centimeter. T at’s dense enough for stars to form. Why does density matter? Ah, because of gravity. It’s gravity that forms a star.
This model shows a buckyball. Its molecules are shaped like a soccer ball.
The Orion Nebula is visible to the naked eye in the night sky.
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14 NATIONAL GEOGRAPHIC EXPLORER
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