Great Conjunction

 

 

A great conjunction is a conjunction of the planets Jupiter and Saturn, when the two planets appear closest together in the sky. Great conjunctions occur approximately every 20 years when Jupiter "overtakes" Saturn in its orbit. They are named "great" for being by far the rarest of the conjunctions between naked-eye planets (i.e. excluding Uranus and Neptune).^[1]

^{https://en.wikipedia.org/wiki/Great_conjunction} 

The spacing between the planets varies from conjunction to conjunction with most events being 0.5 to 1.3 degrees (30 to 78 arcminutes, or 1 to 2.5 times the width of a full moon). Very close conjunctions happen much less frequently (though the maximum of 1.3° is still close by inner planet standards): separations of less than 10 arcminutes have only happened four times since 1200, most recently in 2020.^[2]

https://www.planetary.org/articles/jupiter-and-saturn-great-conjunction-viewing-guide 

Heads-up: Jupiter and Saturn are putting on a once-in-a-lifetime show this December.

The two planets were closer on 21 December than they had been in almost 400 years. With the unaided eye, they almost appeared to touch, separated by less than one-fourth the width of the Moon. They weren’t actually close, of course—Saturn was 733 million kilometers (456 million miles) behind Jupiter. Though the two worlds are now drifting apart each night, they're still putting on a spectacular show that will last through the end of the year.

Time Lapse https://player.vimeo.com/video/491383534?title=0&byline=0&portrait=0 

The exact time of the conjunction was at 1246 on the West Coast, so we missed the perfect alignment.

1730 was prime viewing time here; close enuf for gov work.

 

 

Note Galilean Moons lined up along the ecliptic as we view edge on.