Copied from my post 11 December 2020......
The next Great Conjunction of Jupiter and Saturn will be on the day of the solstice: December 21, 2020. Jupiter-Saturn conjunctions happen every 20 years; the last one was in the year 2000. But these conjunctions aren’t all created equal. The 2020 great conjunction of Jupiter and Saturn will be the closest since 1623 and the closest observable since 1226! On December 21, 2020, Jupiter and Saturn will be only 0.1 degree apart. Some say the pair will look like an “elongated star” on that date.
2002’s extra-close Jupiter-Saturn conjunction won’t be matched again until the Jupiter-Saturn conjunction of March 15, 2080.
At the 2000 great conjunction, 20 years ago, Jupiter and Saturn were near the sun in our sky and difficult to observe. We’re due for a more observable great conjunction. Jupiter and Saturn are up every evening now – not far from the sunset glare – easily visible and exceedingly noticeable as two bright objects near each other.
Why do these great Jupiter/Saturn conjunctions happen every 20 years? Each year, Saturn completes about 12 degrees of its orbit around the sun, whereas Jupiter completes about 30 degrees. Therefore, in one year, Jupiter closes the gap between itself and Saturn by about 18 degrees (30 – 12 = 18 degrees).
In a period of 20 years, then, Jupiter gains 360 degrees on Saturn (18 x 20 = 360 degrees), therefore lapping the ringed planet once every 20 years.
The date schedule is as follows - May 28, 2000, December 21, 2020, October 31, 2040, April 7, 2060, March 15, 2080, September 18, 2100
