The Four-Planet Dance of 2011

If you can find a spot with a completely unobstructed eastern horizon,you can watch an extraordinary sky show from late April 2011 through theend of May. Every morning just before sunrise, four planets combine toform fascinating and ever-changing patterns. This is the tightestgrouping of bright planets that has occurred yet in the 21st century.

Click above to watch a movie of the four-planet dance.Sky & Telescope diagramIf you live in the Southern Hemisphere, you can watch the wholeshow with your unaided eyes, but you will need binoculars to appreciateit properly from mid-northern latitudes. Go outside 45 minutes beforesunrise and scan the eastern horizon until you find a planet. You'resure to spot either Venus or Jupiter first, because these are by far thebrightest of the four.

Venus appears at just about the same spotevery morning in May — just 2° or 3° above the horizon 45 minutesbefore sunrise for observers at mid-northern latitudes, and rising 3°higher each 15 minutes after that. If you pay attention to its location,you can probably continue to see it without optical aid long after theSun rises.

Jupiter is very low at the beginning of May, but itpasses Venus on May 11th and ends the month more than 12° above thehorizon 45 minutes before sunrise. So by mid-May, you're likely to spotJupiter before Venus despite the fact that it's less than one-quarter asbright.

Mercury is the 3rd-brightest planet in the grouping, butit's five to ten times fainter than Jupiter, and quite low in the sky.So you're likely to need binoculars to spot it. It tracks Venus'smotion, staying a few degrees to the lower left of the brighter planetthroughout this period.

Mars is quite faint, just one-hundredthas bright as Venus. It starts May very low in the sky, but catches upwith the Venus-Mercury pairing around mid-month.

A thin crescent Moon joins the show from April 29th to May 2nd and again on May 29-31.

Click here to view a 700-Kb movieof the four-planet dance. After watching the general progression, stepforward and back to see the configuration on any particular morning. Youmay need to install QuickTime to watch the film if you haven't already done so.

Posted by Tony Flanders, March 7, 2011related content: Celestial events, Observing our solar systemlinks: + digg | + del.icio.us | + reddit | + permalink | + rss