The Great Conjunction of 2020

Are you ready for the Great Conjunction on December 21st? This rare astronomical event refers to when the planets Jupiter and Saturn appear close to each other in the sky. This event occurs in an approximately 20-year cycle. The approach will be very close, at a separation of only 6 arcseconds between the planets! The last time these planets appeared this close was in 1623, and the next time will be in 2080. Make sure to take the once-in-a-lifetime chance to observe Saturn and Jupiter simultaneously! The planets will be low on the south-western horizon as the sun sets, so get your, telescopes and binoculars from Orion Telescopes and Binoculars ready for this rare observing opportunity!

At the 2000 great conjunction, 20 years ago, Jupiter and Saturn were near the sun in our sky and difficult to observe. We are due for a more observable great conjunction, and we’ll get one. In November, Jupiter and Saturn were noticeable for their nearness to each other, and they were in the sky when darkness fell.

In December 2020, Jupiter and Saturn will still be easily visible. They’ll be, if anything, even more, beautiful in the western twilight shortly after sunset.

On the 21st December 2020, Jupiter and Saturn will be separated by only 6 arcminutes, the closest conjunction since 1623. Source: Sky Safari 5 Pro.

You’ll recognize Jupiter and Saturn easily from now through the end of the year. Jupiter is brighter than any star. Saturn is not as bright as Jupiter, but it’s as bright as the brightest stars and shines with a distinctive golden color. Also, Jupiter is near Saturn! Saturn is just to the east of Jupiter on the sky’s dome. Unlike the twinkling stars, Jupiter and Saturn both shine steadily.

Over the time between November 21 and the day of the conjunction itself, December 21, Jupiter will travel about 6 degrees and Saturn 3 degrees on the sky’s dome. That movement will mean that Jupiter bridges the 3-degree gap between itself and Saturn.

Whenever Jupiter and Saturn are in conjunction, that is, when they have the same right ascension or celestial longitude, it is referred to as a "Great Conjunction," primarily because unlike conjunctions with the other bright planets, these two don't get together very often. The average frequency of occurrence is merely the product of their sidereal periods divided by the absolute value of their difference.

A sidereal period is defined as the time required for a celestial body within the solar system to complete one revolution with respect to the fixed stars. Saturn's period of 29.65 years multiplied by Jupiter's period of 11.86 years amounts to 351.65. Dividing this value by the difference in their sidereal periods gives us 19.76 years. So, about every 20 years, Jupiter and Saturn will have a rendezvous.

Insight Observatory's remote telescopes ATEO-1 (left) and ATEO-2A (right) will attempt to gather image data of the "Great Conjunction of 2020" from SkyPi Remote Observatory on the evening of December 21, 2020.

Insight Observatory will be attempting to acquire image data of this rare event on the evening of December 21st on its remote Astronomical Telescopes for Educational Outreach (ATEO) from SkyPi Remote Observatory in New Mexico. The conjunction will be extremely low in the southwest part of the sky from our location at SkyPi, however, we are going to give it a try. If you are interested in receiving image data, please contact us.

Sources: Earthsky.org and Space.com