Sky Talk December 2008: A Spectacular Triple Conjunction

Visible in the western sky after sunset on the first evening of December will be a stunning meeting of the three brightest objects in the heavens after the Sun itself—the planets Venus and Jupiter, and the crescent Moon. If it’s clear on that date, you simply must not miss out on seeing this amazing celestial display!

Looking toward the southwestern horizon at dusk on December 1st, you will be greeted by quite a spectacle. Dazzling Venus with radiant Jupiter just 2 degrees to its upper right will be joined by a four-day-old crescent Moon 2 degrees to the upper left of Venus, the trio forming a brilliant celestial conjunction of the three brightest luminaries in the night sky. Adding to the beauty of the scene will be the night portion of the Moon faintly illuminated by Earthshine—light from land and sea masses further to the west where the Sun is still shining, reflected up onto the Moon and back down to us in the darkness.

This lunar and planetary conclave will be a fine sight using just the unaided eye alone. But the view in your Edmund binoculars will be nothing short of spectacular, easily including all three objects with lots of sky around them! Conventional telescopes with their limited fields of view (typically not much more than 1 degree at their very lowest magnification) will be unable to get any two of the three into a single view together. However, the Edmund Scientifics Astroscan’s marvelous 3-degree field of view at 16X will just encompass the trio when at their closest to each other, and show both planets’ non-stellar disks along with lots of craters and other features along the lunar crescent.

For several nights before the conjunction you’ll be able to see the two planets drawing closer together even with the unaided eye, and then following it slowly drifting apart. By Christmas, these restless wanderers will have separated by more than 20 degrees, with Venus having moved higher in the sky to the east and Jupiter lower in the sky to the west. As a bonus, the planet Mercury will make an appearance below Jupiter just above the SW horizon, the two worlds being just 1.5 degrees apart on the 31st. On the night before the conjunction (November 30th) the Moon will be to the southwest of Venus and Jupiter, and on the night after it (December 2nd) will have moved an equal distance to the other side (northeast) of them. Talk about seeing things happening in the sky!

This year’s annual Geminid Meteor Shower—one of the best of all such displays—will unfortunately be washed out by the nearly full Moon when it peaks on the early morning of December 14th.

–James Mullaney
Former assistant editor at Sky & Telescope magazine and author of five books on stargazing.

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