2020, December 20: Jupiter, Saturn on Conjunction Eve

Jupiter, Saturn, December 20, 2020
2020, December 20: In the southwest after sunset, Jupiter is 0.1° below Saturn.

December 20, 2020:  On Great Conjunction Eve, Jupiter is 0.1° below Saturn.  As Jupiter passes Saturn, they are near each other for 3 nights. Great Conjunction Countdown: 1 day!  Mars is farther east in Pisces with the moon between the three planets.

by Jeffrey L. Hunt

Chicago, Illinois:  Sunrise, 7:15 a.m. CST; Sunset, 4:23 p.m. CST.  Check local sources for sunrise and sunset times for your location.

One evening before the Great Conjunction occurs, the planets are low in the southwest as night falls.  Jupiter is 0.1° below Saturn.  When measured in minute fractions of a degree, Jupiter is 471 arcseconds from Saturn.  Tonight, Conjunction evening, and December 22, the planets are very close.  To the untrained eye, they might seem to be the same separation each evening, although Jupiter in its slow-pass meeting with Saturn is in a different orientation each evening.

Depending on your eyesight, you may need a binocular to separate Jupiter from Saturn.  The planets do not merge into a single point.

Their separation is about the same size we see when we look at the Imbrium Basin, a large impact structure, on the moon.  This dark circular region makes up part of the “Man in the Moon” feature and its easily visible when the moon is nearly full and during its waning phases.

The thick crescent moon is in the south.

Mars, December 20, 2020
2020, December 20: Mars is 35° east of the moon. In the starfield, it is 2.8° to the upper left of Zeta Piscium (ζ Psc) and 4.4° to the upper right of Pi Piscium (π Psc).

Mars is farther east from the moon, over halfway up in the southeast.  The gap to Jupiter is over 82°.

The Red Planet is marching eastward.  Each night it appears farther from Zeta Piscium (ζ Psc on the chart) and closer to dim Pi Piscium (π Psc).

Great Conjunction Countdown: 1 day!

Read about Mars during December.

Detailed note: About mid-twilight (45 minutes after sunset), Jupiter is less than 15° up in the southwest.  It is 0.1° (471 arcseconds) below Saturn. Great Conjunction Countdown: 1 day. As the sky darkens further, the thick crescent moon (6.3d, 40%) – about 38° up in the south – is 8.9° to the upper left of δ Aqr.  Because of the moon’s brightness, it might be necessary to shield your eyes from the glare to see the starfield.  Mars is 35° east of the lunar slice and 82.4° of ecliptic longitude east of Jupiter. The Red Planet is 49° up in the southeast among the dim stars of Pisces.  It is moving eastward toward π Psc and away from ζ Psc.  This evening it is 2.8° to the upper left of ζ Psc and 4.4° to the upper right of π Psc. Mars passes π Psc early in the new calendar year.

For more about the Great Conjunction, read our feature article. This is the closest Jupiter – Saturn conjunction since 1623.

Read more about the planets during December.


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Categories: Astronomy, Sky Watching

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