Week of Aug. 19-25, 2018
For the past month or so, four of the five naked-eye planets have been beautifully stretched out across our evening sky: Venus, Mars, Jupiter and Saturn. Mercury, however, has been noticeably absent.
Unlike brilliant Venus, which now dominates our western evening sky, or Jupiter, Mars and Saturn, which shine brightly well after dark, Mercury appears for only a few weeks each year, and even then, quite a bit of effort is required to find it.
Its elusiveness is legendary; it's been said that the great 16th-century Polish astronomer Nicolaus Copernicus — who overturned the long-held notion that the Earth occupied the center of our planetary family — had never actually seen this world with his own eyes.
I wouldn't be surprised since from our terrestrial vantage point, Mercury always appears so close to the sun that it's often lost in its glare. This occurs because Mercury is the innermost world of our solar system and whips around its orbit once every 88 Earth days at a distance of only 36 million miles from the scorching face of the sun. Only when it reaches a significant elongation from the sun can we hope to see it, and this occurs only at dusk or dawn.
If you've never had the pleasure of spotting this fascinating world, now might be a great time to try. The only caveat is that you'll need rise early to see it at dawn.
To find it, head outdoors about an hour before sunrise and begin scanning low in the eastern sky with binoculars. You may spot Mercury as a bright, flickering star only a few degrees above the horizon. Thirty to 45 minutes before sunrise, you should be able to see it with the unaided eye, below the bright twin stars Castor and Pollux, and about the same distance to the lower left of Procyon.
Keep watch from morning to morning as Mercury appears to double its brightness between Aug. 19 and the end of the month. It will, however, remain quite low in the sky, so a relatively flat horizon will be a big help in spotting it.
You can try aiming a small telescope in its direction, but you may be disappointed by what you see. First off, this planet is rather small — barely the size of the continental United States. And second, its appearance near the horizon means that its light must pass through a tremendous amount of distorting atmosphere before reaching our eyes.
If you're fortunate enough to see a relatively steady image, you might notice that Mercury now displays a nearly quarter phase, not unlike the moon does from time to time.
Mercury is a tiny planet and quite different than any other in our solar system. Because it's much too small and close to the sun to sustain an atmosphere, the temperature on its daytime side soars to hundreds of degrees, and the temperature on its nighttime side plunges to hundreds of degrees below zero. And spacecraft photos of this dry, cratered world look remarkably like those of the moon.
If, like the great Copernicus, you've never watched the antics of Mercury, don't miss the show this week and next!
Visit Dennis Mammana at dennismammana.com. To read features by other Creators Syndicate writers and cartoonists, visit the Creators Syndicate website at www.creators.com.