The Great Conjunction of Jupiter and Saturn

Great Conjunction of Jupiter and Saturn (21 December 2020)
Great Conjunction of Jupiter and Saturn (21 December 2020)

On 21 December 2020, Jupiter and Saturn passed a tenth of a degree from each other in what is known as a Great Conjunction. Great Conjunctions are not rare and occur every 20 years. But the apparent separation between the two planets varies with each event and this one was the third closest in over 800 years (1226 and 1623 were closer) but only one of these was visible; the other was lost in the bright glare of twilight.

Great Conjunction with labels of Jupiter and Saturn (21 December 2020)
Great Conjunction with labels of Jupiter and Saturn (21 December 2020)

The images shown here used a 300mm telephoto lens—which is barely sufficient to resolve the rings of Saturn. The rings can be seen as making Saturn appear oval shaped.

The first image is from 1803 MST on 21 December 2020, just a few hours after closest approach. The second image has labels for the brightest moons of Jupiter and Saturn.

Below is an image showing the daily movement of Jupiter relative to Saturn. It is also easy to see the motions of Jupiter’s four largest moons as they appear in different locations for each of the three Jupiter positions.

Three-day sequence of the Great Conjunction of Jupiter and Saturn.
Three-day sequence of the Great Conjunction of Jupiter and Saturn.

Finally, NASA’s Astronomy Picture of the Day has a very nice image of the two planets. Telescope required.

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