Planetary conjunction

The Venus-Mars-Saturn conjunction on August 5th, 2010 (click for a larger view).

A similar conjunction of the Moon, Jupiter, and Venus on December 1, 2008

In the western sky over the next 3 weeks there will be a slow-motion planetary dance, resulting in a conjunction of 3 of our solar system's bright planets. A conjunction simply means a close approach of two or more celestial objects as seen in our night sky. Currently, Venus and Mars are in Leo (Venus makes its own conjunction with the bright star Regulus on July 9th, when the two will be 1 degree, or two full moon widths, apart), with Saturn hanging out in Virgo.

Right now (I'm writing this July 8th), if you look toward the west as soon as the sky gets dark enough, you'll see the very bright white planet Venus. It'll be the brightest object up there. To the upper left will be a fainter, but still conspicuous, spot of light which is Mars. If you hold your fist in front of you at arms length, the two planets will be separated by a distance equal to about two widths of your fist. You'll be able to distinguish Mars by it's reddish or orangey color. Continuing to the upper left (and about 1 more fist distant), is a gold or amber colored object. This one is Saturn.

As the days go by, Mars will slide under Saturn first, reaching its conjunction with the ringed planet on July 30th. The two will be 1.4 degrees apart. Venus catches up a few days after that, when, on August 5, the three will form a triangle, with Mars and Venus both about 3.5 degrees from Saturn. The image at top shows what it will look like. It'll be similar to the Moon-Jupiter-Venus conjunction in December, 2008 (second photo). Click on the images for a closer look.

Subsequent observations will show you even more over the next few days. On August 12th and 13th, the crescent moon will join the group, and Venus and Mars will reach their conjunction on August 16 and be 2 degrees apart as Saturn sinks closer to the horizon. You can gauge this distance by remembering that the full moon is about 0.5 degrees in diameter.

Let's hope that the skies are cloud free a few times between now and the middle of August to allow us to see this spectacle!