December 15, 2020: This evening the moon begins its evening appearance for December low in the southwest after sunset, to the lower right of bright Jupiter. The gap between Jupiter and Saturn continues to close. Meanwhile, Rusty Mars is in the southeast marching eastward in front of the starry background of Pisces.
by Jeffrey L. Hunt
Chicago, Illinois: Sunrise, 7:12 a.m. CST; Sunset, 4:21 p.m. CST. Check local sources for sunrise and sunset times for your location.
The crescent moon begins its evening appearance low in the southwest, as the sky darkens. You’ll need a clear view to the horizon toward the southwest. A binocular will help you find the crescent that is only 2% illuminated.
At this hour, Jupiter is to the upper left of the lunar slice. You may have to look carefully to find it. Saturn is not likely visible, yet, without some help from a binocular.
Tomorrow the moon is closer to the impending conjunction in a little darker sky.
By 30 minutes later (an hour after sunset), Jupiter and Saturn are clearly visible. Jupiter is 0.6° to the lower right of Saturn. This separation is slightly larger than the apparent size of the full moon. Great Conjunction Countdown: 6 days.
The best views of the planet pair occur from 45 minutes after sunset to about 2 hours after sunset. By about three hours after sunset, the planets have set in the southwest.
Bright, rusty Mars is about halfway up in the southeast about an hour after sunset. It continues to march eastward in front of the dim stars of Pisces. With a binocular note that Mars is 1.2° to the upper left of Zeta Piscium (ζ Psc on the chart) and 3.4° to the lower left of Epsilon Piscium (ε Psc). During the month, the planet moves in a direction between Pi Piscium (π Psc) and Omicron Piscium (ο Psc).
Mars then moves into Aries and moves far below Hamal next month.
Read about Mars during December.
Detailed note: Thirty minutes after sunset, the moon (1.3d, 2%) is about 6° up in the southwest – over 18° to the right of Jupiter. Half an hour later, Saturn is 15° up in the southwest 0.6° to the upper left of bright Jupiter. Today, Saturn moved into Capricornus from Sagittarius. Great Conjunction Countdown: 6 days. Mars is 81.9° of ecliptic longitude east of Jupiter, over 46° in altitude above the southeast horizon. In the starfield, the planet is 1.2° to the upper left of ζ Psc and 3.4° to the lower left of ε Psc.
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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