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Red Rivals

August 29, 2012

Two legendary “rivals” are sharing the southwestern quadrant of the evening sky. Although they’re a good distance apart, they’re pretty easy to pick out because they’re both bright orange.

The most famous member of the rivalry is the planet Mars. It’s low in the west-southwest as night falls, and it forms a triangle with two other bright objects to its right — the planet Saturn and the star Spica.

Mars’s rival is far to its upper left: Antares, the brightest star of Scorpius, the scorpion. It’s almost exactly the same color and brightness as Mars, so the two really do look like a matched set.

In fact, the “rivalry” comes from that physical resemblance. Mars reminded ancient skywatchers of the color of blood, so they named the planet for the god of war — Mars in Rome, and Ares in Greece. And since the star in Scorpius looked so much like Mars, it was called Ant-Ares — a name that means “rival of Ares” or, in the Roman version, rival of Mars.

It’s a one-sided rivalry, though. Mars is quite small — only about half as big as Earth. It shines by reflecting sunlight, and gets its orange color from iron-rich sand and rock at its surface. Antares, on the other hand, is a supergiant star — one of the largest stars in the galaxy — thousands of times wider than Mars.

Mars will move closer to Antares over the next few weeks, making the rivalry even easier to see.

We’ll talk about another colorful object — a Blue Moon — tomorrow.

Script by Damond Benningfield, Copyright 2012


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