December 22, 2023: Mercury is between Earth and Sun, known as inferior conjunction. Jupiter and the gibbous moon are celestial companions during nighttime hours.
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. Times are calculated by the US Naval Observatory’s MICA computer program.
Mercury at Inferior conjunction
Mercury is at inferior conjunction between Earth and Sun today at 12:54 p.m. CST. The event is not easily visible as the speedy planet is lost in the sun’s glare. Mercury speeds around the sun about every eighty-eight days, and overtakes Earth about every one hundred, sixteen days.
From Earth, Mercury never strays far from the sun. At its best it rises at about the beginning of morning twilight and appears 10° above the horizon before sunrise or after sunset.
After today’s inferior conjunction, the planet races toward an appearance next month in the eastern morning sky to the lower left of Venus. At mid-month, Mercury climbs to about 11° to the lower left of Venus.
Summaries of Current Sky Events
Summary for Venus as a Morning Star, 2023-24
Here is today’s planet forecast:
Morning Sky
For holiday revelers, bright Jupiter and the gibbous moon are in the western sky after midnight. After midnight and six hours before daybreak, the bright moon, 76% illuminated, is about 15° up in the western sky, 4.5° to the lower right of Jupiter. The pair sets nearly four and one-half hours before sunrise.
By an hour before sunup, brilliant Venus is over 20° above the southeast horizon. The planet steps eastward in front of Libra’s distant stars, below Zubenelgenubi and Zubeneschamali, heading toward Graffias, also known as Beta Scorpii, near the head, Dschubba.
As Earth revolves around the sun, stars slowly make their first appearances in the eastern sky. Graffias and Dschubba are appearing higher each morning. This morning we can see another star, Pi Scorpii (π Sco on the chart). A binocular helps with the view.
Together, Pi, Dschubba, and Graffias resemble Orion’s belt stars, although this trio is dimmer and they are slightly out of a straight line.
Mars is very slowly emerging from bright sunlight into a darker predawn sky, but it is a very challenging view. For practical sky watching, the planet is not visible. It rises forty-two minutes before the sun.
Evening Sky
Jupiter, Saturn, and the moon are the bright planets in the evening sky.
An hour after sundown, the gibbous moon, 83% illuminated, is half-way up in the southeast. 6.7° to the left of bright Jupiter. The moon is moving eastward each evening, compared to the starfield. It is opposite the sun at the Full moon phase on the 26th.
Jupiter, nearing the end of its retrograde, is 11.4° to the lower right of Hamal, Aries’ brightest star, and 14.4° to the upper right of Menkar, part of Cetus. The planet is noticeably west of an imaginary line between the stellar pair. In this moonlight, use a binocular to see the stars.
At 11:37 p.m. CST, Jupiter’s Great Red Spot is visible in the southern hemisphere at the planet’s center. The spot enters the view before 10 p.m. and leaves the scene about an hour into the new calendar day.
Saturn, obviously dimmer than Jupiter, is over 30° above the south-southwest horizon. The planet is slowly moving eastward in front of Aquarius, although the dim stars are washed out by the bright moonlight. Look for Fomalhaut, slightly dimmer than the Ringed Wonder, is about 20° to the planet’s lower left.
During the night, the planets, moon, and stars appear farther westward from Earth’s rotation. Saturn sets five hours after sundown and long before midnight. The moon and Jupiter are south about an hour before Saturn sets. They disappear below the western horizon over an hour before Venus rises.
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