December 20, 2022: The waning crescent moon will be at the lower left of Zubenelgenubi before sunrise. After sunset, look for the five bright planets from the southwest to the east-northeast.
by Jeffrey L. Hunt
Chicago, Illinois: sunrise, 7:14 a.m. CST; Sunset, 4:22 PM CST. Check local resources for sunrise and sunset times for your location.
Daylight has reached the shortest time interval of the year, nine hours and eight minutes. The latest sunrise time (7:18 a.m. CST) begins on the 28the and lasts until January 10e.
The transit times of Jupiter’s Great Red Spot, when it is at the center of the planet in the southern hemisphere: 0:20 UT, 10:16 UT, 20:11 UT. Convert the time to your time zone. In the US, subtract five hours for EST, six hours for CST, and so on. Use a telescope to view the spot. Times are from Sky & Telescope magazine.
Here’s today’s planet forecast:
There is no bright planet in the sky before sunrise this morning. An hour before sunrise, the crescent moon, 11% illuminated, is less than 20° up in the southeast, 4.3° lower left of Zubenelgenubi – meaning “the southern talon of the scorpion.”
The moon is showing earthshine again this morning, an effect of sunlight reflected from the earth, gently lighting up the lunar night. From the Moon, the Earth is almost in full phase and shining brightly.
Zubenelgenubi and the northern claw, Zubeneschamali, are part of today’s Libra. Older maps show one constellation with the creature’s long pincers now reaching over the southeastern horizon. The forehead, Dschubba, is located almost 10° to the east.
Tomorrow morning, the crescent will be over Antares, meaning “the rival of Mars,” making its first morning or heliacal rising following its solar conjunction earlier this month. Try looking for the reddish star above the horizon with binoculars. For the next day or two, it will be visible to the naked eye.
After sunset, look for the five-planet display. In order of brightness, the planets are: Venus, Jupiter, Mars, Mercury, and Saturn. During brighter twilight, Saturn is the challenging sight. Jupiter and Mars are farther east and away from the brighter sky to the west.
Find a location with a clear view of the entire sky from the southwest to the south and back to the east and northeast, but especially toward where the sun sets.
Thirty-five minutes after sunset, brilliant Venus is less than 5 degrees above the southwest horizon. It’s about one binocular field to the right of the southwest tip. The planet is bright enough to be seen without that optical aid.
Mercury is 5.6 degrees to the upper left of Venus. Both are in the same binocular field. Position Venus toward the lower right portion of the field of view. Mercury is then upper left. Can you see Mercury without binoculars?
Saturn, about a third of the way up in the south-southwest, is over 30 degrees to the left of Mercury. Can you see Saturn? You may need to look for it with the binoculars before you can see it without it.
Jupiter is more than halfway to the south-southeast and Mars is to the east-northeast.
As the sky continues to darken, Saturn may come into view before Venus sets.
45 minutes after sunset, Venus is a few degrees above the horizon, theoretically visible but likely blocked by distant Earth features or atmospheric effect. Mercury is at the top left.
Tomorrow (9:31 a.m. CST), when Mercury is east of the sun in the daytime sky, it will reach its greatest angular distance from the sun. It still gains two minutes of setup time, but the brightness starts to fade.
The crescent moon enters the southwestern sky on the 24the. By then, Venus gains another six minutes of setting time, allowing the sky to darken even more before setting. On the 26ethe moon is near Saturn, making identification easier.
Tonight Jupiter is in the south-southeast 45 minutes after sunset and is easy to spot. Saturn is also visible.
Mars is about 20 degrees above the east-northeast horizon. Aldebaran is on the lower right of the planet and Capella is on the upper left. Mars is brighter than the stars.
As the evening progresses, Mercury and Venus disappear below the western horizon, while Saturn, Jupiter and Saturn appear to move further west, marking the ecliptic, the plane of the solar system.
Tomorrow morning, the crescent moon will be near Antares, marking its heliacal rise.