Gas giants bid a fond farewell

December brings the longest nights of the year to people in the Northern Hemisphere. Normally, that would signal favorable conditions for backyard observers. But this year, all of the naked-eye planets cluster near the Sun in our sky, leaving a long stretch of the night without any bright solar system targets.

December’s highlight has to be the dramatic lineup of planets in the early evening sky. While Venus dominates the view toward the southwest after sunset, Saturn and Jupiter add a lovely flair to the scene early this month. Uranus and Neptune, which appear much fainter than their closer cousins, appear higher in the sky and remain visible through the late evening hours. Eventually, the long nights end with fine views of Mercury and Mars before dawn.

Let’s start our tour soon after the Sun sets December 1. A quick look to the southwest reveals Jupiter, Venus, and Saturn strung out across nearly 20° of sky. Jupiter hangs lowest, standing just 7° above the horizon 30 minutes after sundown. It still appears prominent because it shines brightly at magnitude –1.8. The giant world sinks lower with each passing day, however, and disappears into the Sun’s glare during December’s second week on its way to solar conjunction on the 27th.

Venus fares far better. On December 1, it shines at magnitude –3.9 — seven times brighter than Jupiter — from a perch 8° to the giant planet’s upper left. You’ll have to wait for the sky to darken some before you’ll be able to see magnitude 0.6 Saturn, which lies 11° to Venus’ upper left.

Target Venus with binoculars December 2 and you’ll see one of the sky’s finest globular clusters, 5th-magnitude M22 in Sagittarius, less than 1° to the north. A telescope shows the planet’s 12″-diameter disk and 88-percent-lit phase.