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Moon and Companions

March 18, 2018

The vanishingly thin crescent Moon has a couple of companions after sunset this evening — the planets Venus and Mercury. Venus is the brilliant “evening star,” to the right of the Moon. Much-fainter Mercury is about the same distance to the upper right of Venus.

Mercury is tough to see in the early twilight, but its proximity to the brighter lights can help you pick it out.

In fact, this is an especially good time to look for the little world. It’s the closest planet to the Sun, so most of the time it’s hidden in the Sun’s glare. A few times a year, it climbs into view either just before sunrise or just after sunset. For many of those apparitions, though, it stays quite low in the sky, so it’s tough to see even though it can get pretty bright.

Mercury was brightest for this evening appearance a few weeks ago, when it was still quite close to the Sun. It’s been getting fainter as it’s pulled away from the Sun. But because it appears farther from the Sun, it stays in view later, when the twilight isn’t as bright.

Like the Moon, Mercury goes through a cycle of phases. It just passed between Earth and the Sun a few weeks ago, so right now it’s a thick crescent. As it loops back around behind the Sun, sunlight will illuminate more and more of the side that faces Earth. At the same time, though, Mercury will be moving farther from us, so it’ll get fainter. It won’t shine this brightly again until May — this time in the morning sky.

Script by Damond Benningfield

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