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Moon and Companions

October 18, 2012

The Moon has a pair of bright orange companions this evening. The two look so much alike that you might think you’re seeing double.

The companions are the planet Mars and the star Antares — a name that means “rival of Mars.” They’re close to the lower right of the Moon. Antares is slightly brighter than Mars right now, and it stands a little lower in the sky.

While plenty of nightlights twinkle in the sky, not many of them show much color. Most of the stars shine pale white. That’s mainly because they’re so faint — there’s just not enough light to trigger the color receptors in our eyes. So the stars that show any color at all are the ones that look especially bright in our sky.

Antares is one of those. It’s hundreds of light-years away, but it’s also one of the biggest stars in the galaxy, so it shines tens of thousands of times brighter than our own star, the Sun.

The star’s color comes from its temperature. Its surface is thousands of degrees cooler than the Sun, so it shines reddish-orange.

If we could see Antares from close range — as close as the Sun is, for example — we wouldn’t see much color at all. That’s because the star produces some light at all wavelengths. At close range, the light would be so intense that it would saturate the color receptors, so the star would appear white. Only from afar does Antares show its true color — the same color as the planet for which it was named: orange Mars.


Script by Damond Benningfield, Copyright 2012

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