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Triple Play

February 19, 2015

With spring training just getting under way, baseball fans are dreaming of pennants, hitting records, and perhaps even that most elusive of defensive gems, the triple play. They might not get one on the diamond, but there’s a great one in the evening sky the next few nights — a tight grouping of the Moon and the planets Venus and Mars.

This close encounter is made possible by the way the solar system is laid out. The Sun is in the middle, with the planets circling around it in almost the same plane — as if they’re all on a tabletop. The Moon stays close to this plane as well.

Venus, Mars, and the Moon are at different distances from Earth and the Sun, so they move across the sky at different rates.

The Moon completes one loop against the background of stars every 27-and-a-third days. But the motions of the planets across the sky are more complicated. Venus wiggles back and forth between evening and morning sky, and never strays far from the Sun. Mars loops all the way across the starry background, but periodically stops and changes direction. So getting these three worlds together is a complicated task.

But they are close together tonight. The crescent Moon is quite low in the sky as night begins to fall. Venus, the brilliant “evening star,” stands to its upper left, with much fainter Mars directly above Venus. The three will be much closer together tomorrow night, and we’ll have more about that tomorrow.


Script by Damond Benningfield, Copyright 2014

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