Evening planets Saturn and Mars are fading and dropping lower in the western sky as August ticks toward September. Remember when Mars was brighter than Arcturus this spring? Planets. They never sit still. Their light's never constant. We love watching them change, which is why our ancient ancestors knew immediately they were different from the static stars.
From my house, I need to be vigilant to spot Saturn and Mars before they're lost in the treetops. That means getting out about an hour after sunset in fading twilight and finding an open spot where I can look low in the southwestern sky.
You may have noticed that the two have slowly been drawing together over the past few weeks. Mars, much closer to Earth than Saturn, moves more quickly across the sky. It's been 'chasing' slower Saturn for some time now.
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Tonight, the two planets will be 7 degrees apart on either side of Libra the Scales' brightest star, Zubenelgenubi (zoo-BEN-el-je-NEW-bee). The name, a delight to pronounce, is pure Arabic and means 'southern claw'. Libra's stars used to belong to neighboring Scorpius and both it and nearby Zubeneschamali (northern claw) remind of us of times long ago when Libra belonged to Scorpius.
Zubenelgenubi (a.k.a. Alpha Librae) is a double star that observers with keen vision can split with the naked eye. Most of us will find that a pair of binoculars will make the job much easier.
Mars will soon pass its slower brother but not before the two are in conjunction and closest together on the evening of August 25th. Watching two planets pass in the night is fun and instructive - it makes us aware that everything in our solar system's on the move.
This weekend we'll look at another even more amazing planetary conjunction coming up very soon - Jupiter and Venus on August 18.
