Stargazers: Blink and it's gone — spotting ever elusive Mercury
I remember many years ago sitting in Ms. Schnitzer's fourth-grade classroom and getting my first formal taste of astronomy. I always looked forward to hearing her tell us about all the amazing properties of the planets of our solar system.
It was then that I learned about Jupiter, the largest planet with nine moons orbiting it — although today we know it has at least 67 moons. I discovered that Mars appears red, and that Saturn has glorious rings around it. And it was here that I learned that Mercury is the nearest planet to the sun, only 36 million miles from our star's scorching face. That was pretty heady stuff for a 9-year-old back in those "ancient" times.
I had great fun going into the backyard at night to try and spot these distant worlds in the sky. And I was pretty successful, too. But it wasn't until many years later that I actually got a chance to see Mercury.
Part of the delay was because this planet lies so close to the sun that we can never really see it in a completely dark sky. Its 88-day orbit around the sun causes it to swing from dawn to dusk, or from dusk to dawn, just about every month and a half. And this means that one has to be outdoors at just the right time, with a low horizon and good sky conditions, to see 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 occupies the center of our planetary family, had never actually seen this world with his own eyes. Now I can't say whether or not this is true, but it certainly makes sense given what we know about weather conditions in Eastern Europe and how tricky this world is to spot.
Well, the next two weeks will provide us a great opportunity to do what the great Copernicus could never do. In fact, this will be the best opportunity of the entire year to see Mercury from mid-northern latitudes.
To find it, head outdoors shortly after sunset and begin scanning the western-northwestern sky with binoculars. You may spot Mercury as a bright, twinkling "star" only about 10 to 15 degrees above the horizon. About a half-hour after sunset, you should be able to see it with the unaided eye.
You can also try aiming a small, low-power telescope in its direction, but you may be disappointed by what you see. First off, this planet is rather small; in physical dimensions, it's barely the size of the continental United States. And secondly, 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 get a relatively steady image, you might check it out with a higher-powered eyepiece. You'll then notice that Mercury appears not as a circular disk, but as a tiny thin crescent.
It took me many years to finally catch a glimpse of this elusive planet with my eye and a telescope. But believe me — it's well worth the effort!
Visit Dennis Mammana at www.dennismammana.com.
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