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Moon and Companions

February 7, 2018

An impressive array of lights joins the Moon at first light tomorrow: the planets Jupiter and Mars, and the star Antares.

Jupiter is the brightest of those pinpoints, to the right of the Moon. It outshines everything else in the night sky other than the Moon and the planet Venus, so it’s an easy target. And it’ll grow even brighter over the next few months as Earth catches up to it in our smaller, faster orbit around the Sun.

Mars and Antares stack up to the lower left of the Moon, with Mars closer to the Moon.

Mars, too, will grow brighter over the coming months, and for the same reason — we’re getting closer to it. The distance will shrink from about 150 million miles tonight to just 36 million miles in late July, so Mars will shine about 40 times brighter then. In fact, for a few nights it will even outshine Jupiter.

Antares, on the other hand, shines at the same brightness all year long. It’s hundreds of light-years away, so the change in distance as Earth moves around the Sun is negligible — it doesn’t make any difference in how bright the supergiant star appears.

If you look carefully, you may see that Mars and Antares both look orange. The color is harder to see with the bright Moon so close, but if you block the Moon with your hand it becomes more obvious. Because of the similarity in color and, sometimes, brightness, long-ago skywatchers thought of Mars and Antares as rivals, and we’ll have more about that tomorrow.

Script by Damond Benningfield


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