Celestial News: Venus takes dive, Mercury rises
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Monday, March 6, 2017
Jimmy Westlake's Celestial News column appears monthly in the Steamboat Today.
Find more columns by Westlake here.
After dominating our early evening sky all winter, Venus is about to take a nosedive toward the sun and flip-flop into our morning sky. Venus reached its maximum angle away from the sun Jan. 12. Since then, it has rounded the curve in its orbit and will zoom between Earth and the sun March 25, an event called inferior conjunction. Watch the dazzling Evening Star sink lower and lower into the sunset glow with each passing night, losing some of its dazzle as it does.
Venus is now presenting her shadowed nighttime hemisphere to Earth. Through a pair of binoculars or a small telescope, Venus looks like the tiniest sliver of a crescent moon shimmering in the twilight.
It is possible this month to watch Venus all the way up to the date of inferior conjunction, as the planet’s orbit is tilted at its maximum north of the sun. You will need a clear, unobstructed view of the western sky to make this observation. Try to keep track of it each night, and see how close to inferior conjunction you can spot it.
After inferior conjunction, Venus will enter the predawn sky as the Morning Star and shine there through spring, summer and fall 2017.
In the meantime, as Venus drops into the sunset, the planet Mercury is rising out of the sunset fire like a Phoenix. One of nature’s toughest challenges is catching a glimpse of our solar system’s innermost planet, Mercury. Even at its greatest possible elongation, it only can manage to extend some 28 degrees away from the sun. That means Mercury follows the setting sun by only two hours, at most.
The best early evening opportunity to catch Mercury this year occurs within a few days of its greatest elongation April 1. To pinpoint the little planet, try looking low in the western sky between 7 and 7:30 p.m. March 29.
The slender crescent moon will be about one fist width at arm’s length to the upper left of Mercury. The planet Mars will be about the same distance above the moon, but Mercury will appear brighter.
With each successive night, the moon will pull farther and farther from Mercury, leaving the planet alone in the big western sky.
After greatest elongation April 1, Mercury will zoom back toward the setting sun, passing between Earth and the sun during its inferior conjunction April 19.
Professor Jimmy Westlake teaches astronomy and physics at Colorado Mountain College's Steamboat Springs Campus. His "Celestial News" column appears monthly in Steamboat Today. Check out his astrophotography website at jwestlake.com.