After sunset on December 21, Jupiter and Saturn will appear closer to each other in the night sky than they have been since the Middle Ages, appearing to be a dual planet.
“Alignments between these two planets are quite rare, occurring once every 20 years or so, but this conjunction is exceptionally rare due to the closeness of the planets to each other,” the astronomer said. of Rice University Patrick Hartigan in a statement. . “We would have to come back just before sunrise on March 4, 1226, to see a closer alignment between these objects visible in the night sky.
Jupiter and Saturn have been approaching the earth’s sky since summer. From December 16 to 25, the two will be separated by less than the diameter of a full moon.
“On the night of the closest approach, December 21, they will look like a double planet, separated by only one-fifth the diameter of the full moon,” said Hartigan, professor of physics and astronomy. “For most telescopes, each planet and several of its larger moons will be visible in the same field of view that night.”
Although the best viewing conditions are close to the equinoctial line, the Equator is in a prime location, the event can be observed anywhere on Earth, weather permitting. Hartigan said the planetary duo will appear low in the western sky for about an hour after sunset each night.
“The further north a viewer is, the less time they will have to see the conjunction before the planets sink below the horizon,” he said. Fortunately, the planets will be bright enough to be seen at dusk, which may be the best time for many American viewers to observe the conjunction.
“By the time the sky is completely dark in Houston, for example, the conjunction will only be 9 degrees above the horizon,” Hartigan said. “Seeing this would be manageable if the weather cooperates and you have a clear view to the southwest.”
But an hour after sunset, people looking at the sky in New York or London will find the planets even closer to the horizon, at around 7.5 degrees and 5.3 degrees respectively. Onlookers there, and at similar latitudes, would do well to get a glimpse of the rare astronomical sight as soon as possible after sunset, he said.
Those who prefer to wait and see Jupiter and Saturn from this close and higher in the night sky will have to stay until March 15, 2080, Hartigan said. After that, the couple will not make such an appearance until after 2400.