Friday, August 17, 2012

Seldom Seen Mercury

My wife Julie and I have been walking for exercise in the early morning from about 5:50AM to about 6:45AM.  The last couple of mornings (August 17 and 18) we have been enjoying a triple line up from the horizon to about 10 degrees from the zenith of Mercury, Venus and Jupiter.  All of them about equally spaced from each other.  Had it not been cloudy for the couple of mornings prior, we would have glimpsed it before our first sighting.  Mercury will no longer be easily visible by the finish of the week ending August 25, though the other two planets will still be prominent for some weeks to morning observers.

Mercury is the most elusive of all of the naked eye planets since it moves faster in its orbit than any other planet and during must of its orbit appears too close to the Sun to be observed because it is the closest planet to the Sun.  It also appears very low to the horizon so that even distant trees and buildings can hide it, so there will be few places where one can have an unobstructed view.  But for a few days every few months it appears far enough from the Sun to be easily seen given no obstructions: sometimes in the very early morning and at other times in the late afternoon.

Because of the transient nature of Mercury's appearance in the sky, many amateur astronomers have never seen it.  Johannes Kepler (the first person to show that the planets travel in ellipses around the Sun and also the first to precisely figure their orbits) never saw Mercury his entire life!  He figured the details of Mercury's orbit from the observations of Tycho Brahe.  I myself have only personally glimpsed Mercury a few times prior to my latest viewing.

So if you didn't get a chance to see it this time in the morning, late afternoon opportunities will be available in early October of this year.  Another morning apparition will occur a few months after that.  It will keep alternating from morning to afternoon to morning as the year wears on.

Try to spot this fast moving messenger of the classical gods.  If you do you will be in the ranks of the few people who have spotted it. Then you won't suffer the fate of poor Kepler!

Update: My thanks to Shawn Carlson, Executive Director of Labrats Science Education Program, for his kind compliment of this article.

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