Moon and Companions

Moon and Companions

Our eyes are perfectly adapted for life under the Sun. Our star radiates most of its light at a narrow range of wavelengths — those that we can see. So that range is known as visible light.

Those wavelengths make up only a narrow slice of the total range of electromagnetic energy, though. The other wavelengths are well outside the range of human vision. And even if we could see them, most of them are blocked by Earth’s atmosphere.

That includes the infrared — wavelengths that are longer than the eye can see. Water vapor absorbs most infrared wavelengths. So to see the infrared sky, astronomers must place their telescopes up high — on mountains, balloons, aircraft, or spacecraft.

One major infrared target is Antares, the brightest star of Scorpius, the scorpion. The star stands below the Moon as night falls this evening. Brighter Jupiter, the largest planet in the solar system, is about the same distance to the lower left of the Moon. We’ll have more about Jupiter tomorrow.

Antares is a supergiant — it’s much bigger and heavier than the Sun. And at visible wavelengths, it shines about 10,000 times brighter.

But the surface of Antares is much cooler than the Sun. To the eye alone, that makes it look reddish orange. But cooler stars emit a lot of their energy in the infrared. So when you add in those wavelengths, Antares is about 60,000 times brighter than the Sun — a brilliance that’s lost on the human eye.

Script by Damond Benningfield

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