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Spotting Elusive Mercury


Last updated 5/1/2023 at 10:18am

Mercury's elusiveness is legendary.

I remember six decades ago sitting in Miss Schnitzer's fourth-grade classroom and getting my first formal taste of astronomy. I always looked forward to hearing her tell us of all the amazing properties of the planets of our Solar system.

It was there that I learned about Jupiter, the largest planet, with nine moons orbiting it (today we know of 92). I discovered that Mars appeared red, and that Saturn had glorious rings around it. And it was here that I learned that Mercury was the nearest planet to the sun, only 36 million miles from our star's scorching face. Not a big deal to kids these days, but back in those days it sure was!

I had fun going into the backyard at night to try to spot these distant worlds in the sky, and I had pretty good success at it too. But it wasn't until many years later that I actually got a chance to see Mercury.

Part of the delay came 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 must 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 occupied the center of our planetary family – had never actually seen this world with his own eyes. Now I can't say whether 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 provide us with a great opportunity to do what the great Copernicus could never do. In fact, this will be the best evening opportunity of the 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 10-15 degrees above the horizon. About half an hour after sunset, you should be able to see it with the unaided eye.

You can also try aiming a small, low-powered 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 view it with a higher-powered eyepiece. You'll then notice that Mercury appears not as a circular disk but shows phases much like the moon.

It was many years later that I finally caught a glimpse of this elusive planet with my eye and telescope, but it was well worth my effort!

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