On December 21, 2020, the two gas giants of the solar system will appear more closely together in the Earth’s night sky from CE 1226.
On December 21, Jupiter and Saturn will appear one degree apart. This means that two giant planets and their moons will be visible in the same field through a telescope or a small telescope.
In fact, Saturn will appear near Jupiter like some of Jupiter’s moons. This event is called ‘Great Combination’.
The orbits of Earth, Jupiter and Saturn occur alternately every 20 years in this century as these two outer planets appear together in our night sky.
Yet, this is the ‘greatest’ combination between Jupiter and Saturn for the next 600 years, where the two planets will not appear in the sky until 2060.
“Alignments between these two planets are rare, occurring every 20 or once a year, but this combination is very rare due to how close the planets are to each other,” said Professor Patrick Hartigan, an astronomer at Rice University.
“You have to go all the way back before the dawn of March 12, 1226, to see a closer alignment of these things visible in the night sky.”
“On the evening of the closest approximation on December 21, they will look like a dual planet, separated by only 1 / fifth the diameter of the full moon.”
“For most telescope viewers, each planet and several of their largest moons will be visible in the same field that evening.”
Jupiter and Saturn will show less in the western sky about an hour after sunset each evening.
Professor Hartigan said, “The more you look north, the less likely you are to see a glimpse of their combination before the planets sink to the bottom of the horizon.”
“Fortunately, the planets will be bright enough to see twilight, which may be the best time for many U.S. viewers to observe the gathering.”
“For example, once the sky is completely dark in Houston, the connection will be only 9 degrees above the horizon.”
“Weather will help and if you have a blocked view in the southwest it will be arranged to be viewed.”
“But one hour after sunset, people looking up at the sky in New York or London will see the planets closer to the horizon, at about .5.5 degrees and 5.3 degrees, respectively.”
“It would be nice to get a glimpse of the rare astronomical scene there as soon as possible after sunset, for visitors there and at similar latitudes.”
“Those who prefer to wait Jupiter and Saturn together and wait higher in the night sky will have to travel by March 20, 2070.”
“After that, the pair will not show such presence for some time after 2400”.
This article is based on text provided by the National Aeronautics and Space Administration and Rice University.