The planets regularly appear to pass each other in the solar system, with the positions of Jupiter and Saturn being aligned in the sky about once every 20years.
What makes this year’s (December 2020) spectacle so rare?
It has been nearly 400 years since the planets passed this close to each other in the sky , and nearly 800 years since the alignment of Saturn and Jupiter occurred at night , as it will for 2020, allowing nearly everyone around the world to witness this “ great conjunction .”
Conjunctions like this could happen on any day of the year, depending on where the planets are in their orbits .
The date of the conjunction is determined by the positions of Jupiter, Saturn, and the Earth in their paths around the Sun, while the date of the solstice is determined by the tilt of Earth’s axis.
The solstice is the longest night of the year , so this rare coincidence will give people a great chance to go outside and see the solar system.