Jimmy Westlake's Celestial News column appears monthly in the Steamboat Today.
Find more columns by Westlake here.
Ever since August, the dazzling planet Venus has been lighting up our evening sky, but the curtain is about to fall on her most recent performance as our evening star. She has been our constant companion, gleaming in the night during our drives home from work and our after-dinner jaunts. She has given us unforgettable celestial pairings with Jupiter and the moon during the past few months. Now, get ready to say "bye-bye" to our evening star.
Venus has the inside track on Earth as the two planets orbit the sun. Consequently, Venus travels faster in her orbit and gains a lap on us every 584 days. Venus completes her year in 225 days, compared to 365 days for Earth. As each of her evening appearances draws to a close, Venus quickly drops toward the western horizon and zips between Earth and the sun in an event called inferior conjunction. Venus' inferior conjunction occurs March 27 and marks her transition from evening star to morning star. This transition happens quickly, so you have to pay close attention to see it happen. On March 1, Venus was visible for a full three hours after sunset. Today, that time interval shrinks to two hours and 14 minutes, and by March 20, Venus sets only one hour and five minutes after the sun. On March 27, Venus passes the sun and flip-flops into our morning sky, but it will take a week or so before she is far enough from the sun's glare that you can see her gleaming in the sky before dawn. Venus then will remain our morning star for the remainder of 2009.
The next couple of weeks are an excellent time to take a peek at Venus through your telescope or binoculars. In the weeks leading up to and immediately after inferior conjunction, Venus becomes a beautifully thin crescent, large enough to show clearly in binoculars and, if you have clear skies and excellent vision, maybe even with the naked eye. In 1972, just before Venus reached inferior conjunction, I was able to spot the crescent of Venus with no optical aid. It resembled a miniature crescent moon hanging over the setting sun.
Once Venus emerges into our morning sky, she will continue her occasional meetings with the moon and planets. In fact, on the morning of April 22, the waning crescent moon slowly will approach and then eclipse Venus in an amazing sunrise occultation. The coming months are loaded with cosmic moments as Venus plays out her role as our morning star.
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 Web site at www.jwestlake.com.