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Moon and Spica

January 22, 2014

The Moon passes breathtakingly close to a bright star in the wee hours of tomorrow morning: Spica, the leading light of Virgo. At their closest, they’ll be separated by about the width of the Moon itself. And the bright orange planet Mars looks on from just above them.

Spica is one of only a handful of bright stars that can have such close encounters with the Moon. That’s because the Moon follows a narrow path across the sky — within a few degrees of the Sun’s path, known as the ecliptic. The stars all maintain fixed positions relative to the ecliptic, so only a few of them can greet the Moon each month.

But not all monthly encounters with the Moon are the same, because the Moon’s path is tilted slightly with respect to the ecliptic. So some months the Moon passes quite close to stars like Spica, and others it gives them a wide berth.

This month, the geometry is right for an especially close passage. As they climb into good view after midnight, Spica and the Moon will be separated by about a degree — less than the width of your finger held at arm’s length. At their closest, around 3 or 4 a.m. Central Time, they’ll be just half a degree apart. The exact separation depends on your location. They’ll appear a little closer together from northern latitudes than southern ones.

After that, the Moon will slowly move away from Spica, and they’ll be a degree or two apart at first light — headed toward another good encounter just four weeks later.


Script by Damond Benningfield, Copyright 2013

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