Jimmy Westlake: July’s parade of planets
July 2, 2010
Steamboat Springs — Don't be alarmed if you are sunbathing on a South Pacific isle July 11 when suddenly the sun disappears and the stars pop out at midday. It's just a total eclipse of the sun.
Many of the islands in the South Pacific will experience about five minutes of the rare darkness produced as the shadow of the moon races across the surface of the Earth at nearly 1,000 miles per hour. Unfortunately, none of this eclipse will be visible from the continental U.S. We must wait until Aug. 21, 2017, before we fall under the moon's total shadow, but there are plenty of other celestial events going on this July to keep us looking up.
All five of the bright naked-eye planets will be visible this month, four of them at once in our early evening sky. Venus, Mars and Saturn have been sprawled across our early evening sky for weeks, but as we move through July, these three planets begin to huddle together, tighter and tighter.
Let's start with the evening of July 9, when the brightest of all the planets, Venus, glides only 1 degree north of the bright star Regulus in Leo the Lion. Venus will outshine Regulus by a factor of 150, but the two bright objects shining side by side in the evening twilight will be quite an eye-catcher. Look west between 9:30 and 10 p.m. July 9.
Then, after the hot July sun sets July 14, a cool crescent moon will join Venus in a breathtaking close conjunction while the less bright but still easy-to-spot planets Mars and Saturn shine to the moon's upper left. The next night, July 15, the celestial players return for Act 2, but this time, the moon shines just below Mars, with Venus to its right and Saturn to its left. On the third night, July 16, the moon appears closest to Saturn as it continues its eastward motion through the stars.
About the time the three evening planets set in the west, another bright planet pops up above the eastern horizon. It's Jupiter, second in brightness only to Venus. Watch for Jupiter to make its appearance at about midnight in late July.
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Meanwhile, the rapidly moving and diminutive little planet Mercury will peep out of the evening twilight toward the end of the month, joining the trio of Venus, Mars and Saturn to form a rare quartet of bright planets. You'll need an unobstructed view of the western sky clear to the horizon to spot Mercury, but try looking between 9 and 9:30 p.m. on the evening of July 30. That's the night Mars shines just 2 degrees below Saturn with Venus only 7 degrees to their lower right. Mercury shimmers another 18 degrees (about a hand span) to Venus' lower right.
Professor Jimmy Westlake teaches astronomy and physics at Colorado Mountain College's Alpine Campus. He is an avid astronomer whose photographs and articles have been published all across the world. Check out Jimmy's astrophotography website at http://www.jwestlake.com.