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Moon and Venus

StarDate: 
March 6, 2016

The morning sky is about to lose its guiding light. Venus, the “morning star,” soon will pass behind the Sun. It’s moving closer to the Sun, so it’s getting lost in the Sun’s glare. It won’t return to view until July — this time in the evening sky.

Because of the relative orbits of Venus and Earth, Venus traces the same path across the sky every eight years. In other words, any time you see Venus, you can know that it stood at the same spot in the sky eight years earlier, and will appear in that spot once again in eight years more.

Over those eight years, Venus makes five appearances in both morning and evening skies. And each of those appearances is almost identical to the one eight years before.

Venus’s transition from morning to evening sky takes longer than the other way around, because it happens when Venus is on the opposite side of the Sun. So even though it’s moving at a steady orbital speed, it takes the planet longer to cover a given angle on the sky as seen from Earth. So when it disappears in the morning twilight, it stays out of sight for a long time.

Right now, Venus is quite low in the eastern sky as twilight grows bright. Tomorrow, it’s close to the right of the crescent Moon. You need a clear horizon to spot them. And skywatchers in the far-southern latitudes of the United States will have a better view than those in the north, where Venus is already tough to spot as it closes another cycle as the “morning star.”


Script by Damond Benningfield

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