Thursday, January 15, 2015

Tonight's Sky for January 15: Mercury at its Best


Want to join a small club of people who have seen the planet Mercury? Well, here's your chance as the first planet from the Sun will be making its best appearance of the winter this evening.

Of all the Classical Planets (those known to the Ancient Greeks and Romans), Mercury is by far the hardest to spot because, as seen from Earth, it never gets very far away from the Sun. As a result, Mercury is often obscured from view by the Sun's glare.

As of today, Mercury has reached a point in its orbit called greatest elongation, which is a fancy way of saying that, as seen from Earth, Mercury is as far from the Sun as it will get on this orbit. How good is it? So good that Mercury sets about an hour and a half after the Sun! So good that, even 30 minutes after sunset, Mercury is still about 10 degrees up from the horizon. To simulate, hold your fist vertically at arm's length. While that may not seem overly high, for elusive Mercury, that's quite good.


So, take a moment or two, go out just after sunset, and try to spot Mercury. If you are successful in spotting the speedy planet, you are accomplishing something that the great astronomer Nicolaus Copernicus (who rediscovered the idea of a sun-centered solar system) supposedly never did.

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