Dec. 21 marks the Winter Solstice, bringing the shortest amount of daylight and the longest night. This year it coincides with the Great Conjunction, when Saturn and Jupiter appear at their closest.

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Conjunctions occur about every 20 years, but this will be the closest the planets appear since 1623. This happens because Saturn takes 30 years to orbit the Sun, while Jupiter does the trip in 12 years. Jupiter catches up with Saturn about every 20 years. Jupiter and Saturn have been fairly close since the summer and are quite visible in the southern sky.

The best strategy to view the Great Conjunction is to start looking low in the southwestern sky about 45 minutes prior to the sunset in your area. While it will be visible by the human eye, binoculars or a telescope will provide a good view of some of the moons of both planets. This won’t be visible long, though. Both planets set soon after sunset. The full show starts around Dec. 16, when both planets appear close to each other.

During the Great Conjunction, Saturn and Jupiter will be only 0.1 degree apart. Despite that sounding close, the planets are actually hundreds of millions of miles apart.

This rare event has been called “The Christmas Star” because of the timing. Some researchers theorize a similar conjunction could be responsible for the star of Bethlehem in the Christmas story.

If you are into astronomy or just want to see something cool in the sky, don’t miss this rare opportunity. The next time the Christmas Star will be visible is 2080.

— John Wroblewski, online writer