by William J. Bechaver
EARTH — It seems like it was only last week I was writing about catching a sight of Mercury in the morning sky.
But two months have passed, and in that time, Mercury has swung all the way around the far side of the sun, and is now making a decent appearance in the evening sky.
What’s more, this week it will be joined by Saturn, to make an interesting pairing of the two extremes. Mercury is tiny, and the closest planet to the sun. Often lost in the sun’s glare, sighting it is usually difficult.
In contrast, Saturn is the naked eye planet furthest from the sun, and including its ring system, it is the largest planetary target to be viewed.
This week, the two will join each other in the south western evening sky. They will appear closest together on the evening of Tuesday, November 28. Just after sunset, go out and look just south of where the sun sank. At that time, just a good distance above the horizon, try to spot brighter Saturn, appearing before any stars will emerge from the twilight glow.
As the evening progresses, about an hour later, Saturn should be easily discernable, with tiny and dimmer Mercury close by. Only about three degrees will separate the two objects, and the best time to view will be around six o’clock, while the sky is getting dark enough, yet the two are far enough above the horizon not to be lost in the evening haze.
The two will set less than an hour later, so timing will be key for spotting the rare pair.
During the sighting, Mercury is approaching us on the nearer side of the sun. It will be slightly closer to Earth than we are from the sun.
Mighty Saturn, however, is on the far side of the sun in its orbit, and lies an astounding eleven times further than the tiniest planet. It is currently over a billion miles distant from us. It is due to that great distance, and its appearance near the glow of the sun, that makes it more difficult to spot this time of year.
In the weeks to come, we’ll take a closer look at Saturn through the eyes of NASA’s Cassini mission. The mission came to an end last month, but the final data it sent back is still being analyzed, and we are still learning more from it every day.
But for now, get out there next Tuesday evening, and try to spot it, along with evasive Mercury. In the coming weeks, we’ll outrun Saturn in it’s orbit, and it will slowly sink behind the sun, until it’s lost in the glow by Christmas.
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William J. Bechaver is the director of SPACE • Spanish Peaks Amateur Cosmos Enthusiasts, the premier Astronomical Society for Southern Colorado and Northern New Mexico.