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‘Great Conjunction’ 2020: Jupiter And Saturn Will Overlap Each Other In The Sky On Dec. 21 To Appear Like One Huge ‘Christmas Star’

By • December 20, 2020 1:46 pm

The world will soon witness two planets align — a rare celestial occurrence last seen in the Middle Ages —  as Jupiter and Saturn, is set to line up and appear like a double planet in the sky starting December 21.

The once-in-a-lifetime phenomenon will occur after sunset from Monday, which also marks the beginning of the winter solstice, the period with the fewest daylight hours of the year, though the Jupiter-Saturn alignment will also be visible in the night sky all through the Christmas night.

“Alignments between these two planets are rather rare, occurring once every 20 years or so, but this conjunction is exceptionally rare because of how close the planets will appear to one another,” Rice University astronomer Patrick Hartigan said in a statement.

“You’d have to go all the way back to just before dawn on March 4, 1226, to see a closer alignment between these objects visible in the night sky,” Hartigan added, which means the celestial occurrence last occurred 794 years back.

Closest position on December 21

Although Saturn and Jupiter will be closest on Monday night, he noted that “they’ll appear very close together until Dec. 26.”

“From Dec. 16-25, the two will be separated by less than the diameter of a full moon.

“On the evening of closest approach on Dec 21 they will look like a double planet, separated by only 1/5th the diameter of the full moon,” said Hartigan, a professor of physics and astronomy.

“For most telescope viewers, each planet and several of their largest moons will be visible in the same field of view that evening.”

While spectators closer to the equator will have the best viewing conditions of the planetary duo, Hartigan noted that the Jupiter-Saturn pair will be visible from nearly anywhere on the planet — but will appear “low in the western sky for about an hour after sunset each evening” in the US.

“The further north a viewer is, the less time they’ll have to catch a glimpse of the conjunction before the planets sink below the horizon,” he said. Fortunately, the planets will be bright enough to be viewed in the twilight, which may be the best time for many U.S. viewers to observe the conjunction,” the Rice University astronomer added.

Next occurrence: Year 2400

“By the time skies are fully dark in Houston, for example, the conjunction will be just 9 degrees above the horizon,” Hartigan added, noting that “viewing that would be manageable if the weather cooperates and you have an unobstructed view to the southwest.”

“But an hour after sunset, people looking skyward in New York or London will find the planets even closer to the horizon, about 7.5 degrees and 5.3 degrees respectively. Viewers there, and in similar latitudes, would do well to catch a glimpse of the rare astronomical sight as soon after sunset as possible,” he said.

Meanwhile, Hartigan said “those who prefer to wait and see Jupiter and Saturn this close together and higher in the night sky will need to stick around until March 15, 2080” or in 60 years.

“After that, the pair won’t make such an appearance until sometime after the year 2400,” he added.

According to NASA, the alignment has been expected for a long time as Jupiter orbits the sun every 12 years, and Saturn’s orbit takes 30 years. The space agency noted that every couple of decades, Jupiter also laps Saturn.

“Dancing across the night sky, Jupiter and Saturn will make their show-stopping move on Dec. 21 when they align to form what’s known as the ‘Great Conjunction.’ Here’s how you can watch: https://go.nasa.gov/37nMVul,” NASA said.

Steeve Strange

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