There are still 24 days left in 2020, so of course there’s time for something that hasn’t occurred in nearly 800 years.
Jupiter and Saturn, the two largest planets in the solar system, will soon line up and look like a double planet, a sight not seen since the Middle Ages.
The rare celestial event will occur after sunset on Dec. 21, 2020, the start of the winter solstice.
“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.”
Jupiter orbits the sun every 12 years, while Saturn’s orbit takes 30 years, and every couple of decades, Jupiter laps Saturn, according to NASA.
A poster on Reddit created a nifty little graphic to show what’s coming.
reddit.com
The two gas giants have been getting closer and closer since the summer and 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.”
Hartigan said the best viewing conditions will be near the equator, but noted that the event will be observable anywhere on Earth. He also said the planetary duo will appear low in the western sky for about an hour after sunset each evening.
“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, although he added that the planets will be bright enough to be seen in twilight, which may be the best time for many U.S. viewers to observe the alignment.
“By the time skies are fully dark in Houston, for example, the conjunction will be just 9 degrees above the horizon,” Hartigan said. “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,” Hartigan said in his statement.
He also 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. After that, the pair won’t make such an appearance until sometime after the year 2400.”