You are here

Red Rivalry

February 8, 2018

Two legendary “rivals” are huddling close together in the dawn sky this month. Both shine bright orange, making them easy to find. And the Moon passes by them tomorrow, so they’re even easier to pick out.

The ancient rivalry between Mars and Antares comes from their resemblance. Mars reminded ancient skywatchers of the color of blood, so they named the planet for the god of war: Ares in Greece, and Mars in Rome. Since the heart of the scorpion looked so much like Mars, it was called Ant-Ares, which means rival of Ares or, in the Roman version, rival of Mars.

Mars is colored by iron-rich dust that covers much of its surface. The dust is generally orange or yellow-orange. Combined with darker areas of exposed rock, that gives the planet an overall orange appearance.

Antares looks orange because of its temperature. Like all stars, it’s a glowing ball of gas. The color of that gas depends on its temperature. Cool stars shine red or orange, while hot stars are blue or white. Antares is at the cool end of that range, so it shines bright orange.

As Mars travels against the starry background, it passes by Antares once every couple of years. In a few days it’ll pass within about five degrees of Antares — about half the width of a fist held at arm’s length. They’ll be in the south at first light, with Antares to the lower right of Mars. As a bonus, the brilliant planet Jupiter will stand to the upper right of these colorful celestial rivals.

Script by Damond Benningfield


Get Premium Audio

Listen to today's episode of StarDate on the web the same day it airs in high-quality streaming audio without any extra ads or announcements. Choose a $8 one-month pass, or listen every day for a year for just $30.