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Mercury in the Evening

November 29, 2010

Mercury is playing the tease the next few evenings. The planet’s in the southwest at sunset, and comes into view as the sky begins to darken. But it’s so low that it’s hard to find.

Mercury is the closest planet to the Sun, so the angle between the two as seen from Earth is never very large. At best, Mercury is in view for a little while after sunset or before sunrise, and even then it’s usually immersed in the glow of twilight.

That makes Mercury a difficult planet to study. Optical telescopes have little luck making out features on its surface. They couldn’t even tell us how fast Mercury turns on its axis.

But radio telescopes are more successful. They’re not blinded by the sunlight, so they can see more detail. They revealed that Mercury turns on its axis every 59 days. They’ve also found evidence of ice at Mercury’s poles.

The best view of all comes from spacecraft. Two craft have each flown past Mercury three times. They’ve mapped most of the planet’s surface, and provided important details on its composition and structure. And one of those craft, called Messenger, will enter orbit around Mercury next year -- giving us a non-stop look at this elusive planet

For now, if you’re in the southern half of the country, look for Mercury quite low in the southwest beginning about 30 minutes after sunset. It looks like a bright star, but you may want to use binoculars to help you find it through the fading twilight.


Script by Damond Benningfield, Copyright 2010


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