Jimmy Westlake's Celestial News column appears monthly in the Steamboat Today.
Find more columns by Westlake here.
There are only five planets that can be seen easily with the unaided eye. They are Mercury, Venus, Mars, Jupiter and Saturn. All five are among the brightest objects shining in our nighttime sky, but they are not equally easy to locate. The only one that requires making a special effort to see is Mercury, the innermost planet in our solar system.
Mercury is a challenge to see for two reasons. First, it moves very fast as it circles the sun, completing an orbit in only 88 days. Consequently, Mercury moves in and out of visibility in a matter of only a few days, whereas the other planets remain visible for months on end. This rapid movement is the reason that ancient skywatchers named this particular planet for the swift messenger god with winged sandals. The second reason Mercury is challenging to locate in the sky is because it never wanders very far from the sun. You must either catch a glimpse of it just before the sun comes up or just after the sun goes down and it is, therefore, never visible in a completely darkened sky. So, the bottom line is this: to spot Mercury with your unaided eye, timing is everything.
It just so happens that the timing is perfect right now to see Mercury in the evening sky without much effort. During the first two weeks of February, Mercury will be an easy target in the western sky about 45 minutes to an hour after sunset. The brilliant planet Venus, also shining in our evening sky, can help guide you right to Mercury. Venus will be the first planet to pop into view after sunset in the southwestern sky. Once you've located Venus, hold your clenched fist at arm's length and scan the sky one fist-width to the lower right of Venus at the 5:00 position. After the twilight has faded sufficiently, Mercury will be easy to see, twinkling in the colorful sunset glow.
With a medium-sized telescope and a clear sky, you should be able to glimpse the phase of Mercury, which will change from a fat gibbous on Feb. 1 to a quarter phase by Feb. 7 to a thin crescent by Feb. 10.
Many famous astronomers, including Copernicus, are said to have never seen the planet Mercury with their own eyes. You can get one up on Copernicus this week by spotting Mercury for yourself.
Jimmy Westlake teaches astronomy and physics at Colorado Mountain College's Alpine Campus. He is an avid astronomer whose photographs and articles have been published on the Web sites of CNN.com, NASA's "Astronomy Picture of the Day," Spaceweather.com, Space.com, Discover.com, and in Sky & Telescope, Astronomy, Night Sky, Discover, and WeatherWise magazines.