Thursday, March 10, 2005

Mercury, the moon, and more links

For as long as I can remember I have been an avid watcher of the skies. But until a few years ago there was one thing I had never seen.

Mercury is the closest planet to the sun. It orbits the sun in just under 88 days, but rarely strays far enough from it in the sky to escape the glare of sunrise or sunset. There are only a few times each year when you have a good chance to see Mercury, and then your chance lasts only a few days. Now is one of those opportunities.

For the next few days Mercury will appear low in the west just after sunset. Jack Horkheimer talked about it on this week's show, and here is a graphic used on the show that depicts the western horizon shortly after sunset on Saturday, March 12th. On that evening the moon will be a thin crescent, a slim fingernail of light about a third of the way between the western horizon and the Pleiades (that little, dipper-shaped group of stars near the top of the picture - not to be confused with the Little Dipper!) Watch for the faint, ghostly image of the entire moon to appear as a result of earthshine, the reflection of sunlight off of the side of the Earth facing the moon.

With a little luck, a clear sky, and an unobstructed view of the horizon you may actually see a very thin crescent moon very close to Mercury just after sunset on the evening of March 11th. Go to the Heavens-Above website, punch in your location, go to the Whole Sky Chart, set the date to March 11 and the time to about 17:30, and get a sense of the relative locations of the sun, moon, and Mercury. And I hope you get to see it! If you don't...well, it is said that Nicolaus Copernicus never managed to see Mercury in his entire life, so you're in good company!

By the way, I've added a "Site Links" feature to the bottom of the right-hand margin, with links to non-blog sites that I visit (and reference) fairly often. Check it out!

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