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Mars and Aldebaran

July 12, 2011

For the most part, the night sky is pretty colorless -- a bunch of little points of white sparkling against a dark background. So when you do see a dab of color, it stands out. And when you see two dabs of color standing close together, it attracts your attention like a neon sign.

That's the case right now with Mars and Aldebaran. They're in good view in the east at first light. And tomorrow, they line up parallel to the horizon, separated by a little less than the width of your fist held at arm's length. Mars is to the left, with brighter Aldebaran to the right.

Both of them shine with a definite orange hue. But they produce it in quite different ways.

Aldebaran is a star. The nuclear reactions in its core produce energy that eventually makes it to the star's surface, where it radiates out into the universe. Aldebaran is nearing the end of its life, so its surface is puffy and cool -- a mere 8,000 degrees Fahrenheit. That temperature is what controls the star's color -- cooler stars like Aldebaran shine orange or red.

Mars, on the other hand, is a planet -- a ball of rock like Earth. It produces no light of its own, but shines by reflecting sunlight. Much of the Martian surface is coated with a powdery layer of iron oxide -- rust -- a compound with a reddish-orange color. There's enough of it to give the planet an overall orange appearance -- a bit of color against the blackness of the night sky.

Tomorrow: first port of call.


Script by Damond Benningfield, Copyright 2011


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