Updated: September 28, 2022
Jupiter and Saturn rendezvous about once every 20 years, but tonight from the Earth’s point of view, they will appear closer than they have since 1623 when Galileo was alive.
It’s a heavenly end to a disastrous 2020, with the “great conjunction” of these two planets forming what many are calling the “Christmas Star.”
In 1623, 397 years ago, many could not see the astronomical event because of the close proximity to the glare of the sun and low altitude above the horizon. So for skywatchers, the last observable time these two planets were this close — creating almost a single bright star — was nearly 800 years ago on March 5, 1226.
Tonight, skywatchers don’t need a telescope or binoculars to view the “Christmas Star.” The two planets will be visible to the naked eye. Look toward an unobstructed part of the southwestern sky about 45 minutes to an hour after sunset. The planets set below the horizon quickly so earlier in the night is better.
There are several free apps, including Star Map Tracker, to help you locate Jupiter, Saturn, the stars and constellations in the night sky. Space.com also has put together a list of webcasts for those who can’t go outside.
Jupiter and Saturn will appear just one-tenth of a degree apart, or about the thickness of a dime held at arm’s length, according to NASA.
The great conjunction doesn’t happen often because Jupiter and Saturn are the two slowest moving planets. Jupiter requires nearly 12 years to circle the heavens with a year spent in each zodiacal sign. Saturn, which has a larger orbit, takes 29.5 years to circle the sun.
This year the astronomical event just happens to occur on the winter solstice, the longest night of the year.
Original source: https://mauinow.com/2020/12/21/tonights-christmas-star-shines-with-jupiter-and-saturn-last-appearing-this-close-397-years-ago/