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Moon and Antares

March 5, 2010

Even on a late winter's day, you notice a couple of things when you step out into the sunshine. The Sun is bright, and it's warm. The "bright" part comes from a part of the electromagnetic spectrum known as visible light -- a narrow range of wavelengths that our eyes can see. And the "warm" part comes from infrared light -- wavelengths that are longer than the human eye can detect.

Most of the Sun's energy output is in the form of visible light. But that's not true for all stars. In fact, a jumbo star that appears near the Moon the next couple of mornings emits most of its energy in the infrared.

Antares is the leading light of Scorpius, the scorpion. It's low in the south at first light tomorrow, to the lower left of the Moon. It'll be a little closer to the right of the Moon on Sunday morning.

Antares is a supergiant -- one of the biggest stars in the galaxy. If it took the Sun's place, it would swallow up Earth and extend far beyond the orbit of Mars.

Because Antares is so puffed up, its surface is thousands of degrees cooler than the Sun's, so it looks orange. And if you lined up Antares and the Sun at the same distance, Antares would look about 10,000 times brighter.

But cooler stars like Antares radiate most of their energy in the infrared. So when you add that in to the mix, Antares is about 60,000 times brighter than the Sun. You wouldn't be able to see that difference, but you certainly could feel it.

Script by Damond Benningfield, Copyright 2010

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