December 17, 2024: A close Mars-Moon conjunction occurs overnight. Before sunrise, Mercury emerges from brighter sunlight.
by Jeffrey L. Hunt
Chicago, Illinois: Sunrise, 7:13 a.m. CDT; Sunset, 4:21 p.m. CST. Check local sources for sunrise and sunset times. Times are calculated by the US Naval Observatory’s MICA computer program.
Mercury Emerges
Before sunrise during the next several mornings, Mercury is visible in the southeastern sky. It emerges from brighter twilight for its final appearance of the year.
Mercury is near the brighter stars of Scorpius as they reappear in the morning after their solar conjunction. The arachnid’s claws, Zubenelgenubi and Zubeneschamali, are higher in the sky to the upper right.
At 45 minutes before sunrise, Mercury is nearly 10° above the southeast horizon, 3.6° to the lower left of Graffias and 6.1° to the left of Dschubba, two stars in the Scorpion. Use a binocular to initially locate the planet. It might be visible to the unassisted eye in a very clear sky.
Mercury continues to brighten as it reaches greatest elongation on Christmas morning, when the planet is farthest from the sun that we see it.
Mars-Moon Conjunction
After sundown, Venus, Saturn, and Jupiter are along an arc from the southeast to the east-northeast. Mars joins the scene about the time Venus sets over three hours after sundown. By four hours after sunset, the bright gibbous moon, 91% illuminated, is about 15° above the east-northeast horizon and 3.0° above Mars.
As Earth rotates during the night, Mars and Moon appear higher in the sky, although the lunar orb revolves slowly eastward. As the calendar day ends, the pair is over halfway up in the east-southeast. The moon is only 1.5° above Mars.
After midnight on the 18th and at 3:15 a.m. Central Time, the moon passes 0.5° (one full-moon diameter) above Mars. The Beehive star cluster appears in the same binocular field with Mars and the moon, although it is muted by the moonlight that washes across the field of view.
Sky watchers in northeastern Canada see the moon occult or eclipse the planet.
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