How to see the rare 'Christmas Star' over Arizona

Arizona Republic

Jupiter and Saturn will appear so close together after sunset on Monday that they will look like a single, bright star.

The phenomenon, known as the Great Conjunction, only happens about once every 20 years.

This year is special because the planets will be the closest they have been in 400 years. Local astronomers say this is a sight you shouldn't miss.

"It's visually impressive," said Patrick Young, an associate professor at Arizona State University's School of Earth and Space Exploration.

The Great Conjunction has been dubbed the "Christmas Star" because of the theory that the Star of Bethlehem could have been the conjunction of the two planets.

Astronomers recommend going outside a couple of nights in advance of Dec. 21 so you get used to spotting Jupiter and Saturn. The planets appear in the southwest after sunset. Jupiter is the brighter planet; Saturn is fainter and may appear gold.

Each evening leading up to Monday, the planets will appear to be closer together in the sky, said Kevin Schindler, the historian at Lowell Observatory in Flagstaff. If you use binoculars or a telescope, you will be able to separate them.

The most important thing to know: You will have a narrow window to see the Great Conjunction because the planets quickly set on the horizon after dark. You will have to wait until the sky is dark enough to see the planets, but even a couple of hours after sunset will be too late. Keep in mind sunset is around 5:30 p.m. in Arizona.

Schindler predicts that 5 p.m. to 7 p.m. will be the "golden time" for viewing the Great Conjunction over the state.

Jupiter, the larger planet at center, and Saturn, just above Jupiter, are seen in the sky outside of Sedona on Dec. 18, 2020. On Dec. 21 they will appear almost as one object, the closest they've been seen together in 800 years.

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While Great Conjunctions happen about once very 20 years, the next time Jupiter and Saturn will be this close during a Great Conjunction won't happen for another 60 years: on March 15, 2080 to be precise.

"Seize this opportunity. Don't let it pass," said Adam Block, who works at Steward Observatory in the University of Arizona's Department of Astronomy. "This is really something you won't see again for some time."

If you want to stay indoors, you can still see the Great Conjunction online. Lowell Observatory will hold a virtual viewing online from 5 p.m. to 6:30 or 7 p.m. See the observatory's website here.

Reach the reporter at anne.ryman@arizonarepublic.com or 602-444-8072. Follow her on Twitter @anneryman.

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