2025, December 7: Mercury at Greatest Elongation; Jupiter and Moon in the West

December 7, 2025: Mercury reaches greatest elongation before sunrise. Find it low in the southeast while Jupiter and the waning gibbous moon shine in the western sky.

Venus and Mercury, November 7, 2020
2020, November 7: About 40 minutes before sunrise, Mercury – low in the east-southeast – is 5.1° to the left of Spica. Brilliant Morning Star Venus gleams from higher in the sky.

by Jeffrey L. Hunt

Chicago, Illinois: Sunrise, 7:05 a.m. CST; Sunset, 4:20 p.m. CST.  Times are calculated by the US Naval Observatory’s MICA computer program. Check local sources for sunrise and sunset times.

Mercury at Greatest Elongation

Mercury, inferior conjunction, November 20, 2025
Chart Caption – 2025, November 20 and December 7: The orbital views of Earth and Mercury show the innermost planet between Earth and Sun followed by its greatest elongation.

Today Mercury reaches its maximum separation from the sun, known as greatest elongation. The Sun–Earth–Mercury angle is 20.4°. Even at its best, Mercury is always seen during twilight from mid-northern latitudes.

From our changing line of sight to the plane of the solar system near the horizon during twilight, Mercury presents its most favorable views during spring evenings and autumn mornings.

This morning apparition began when Mercury passed between the sun and Earth on November 20th, moving into the morning sky west of the sun. (When a planet rises before sunrise, it is west of the central star.) Today the planet is farthest from the sun.

Jupiter, Moon, December 7, 2025
Chart Caption – 2025, December 7: Jupiter, moon, and Pollux form a compact bunch in the western sky before sunrise.

This morning Mercury rises 108 minutes before sunrise. By 45 minutes before sunup, it is nearly 10° above the southeast horizon, below the Scorpion’s claws — Zubenelgenubi and Zubeneschamali. Find a clear view toward the southeast and initially locate Mercury through a binocular, then look without the optical assist. The planet’s visibility is muted by the colorful hues of mid-twilight and the thicker atmosphere near the horizon that dims and blurs celestial bodies.

After greatest elongation, Mercury slowly retreats into morning twilight, losing about 10 minutes of rising time relative to sunrise during the next week. As it descends, it brightens. By Christmas it loses over 40 minutes of rising time. Continue to follow Mercury into bright morning twilight.

Mercury passes behind the sun at superior conjunction on January 21st, then reaches its first evening greatest elongation of 2026 on February 19th. On that evening, Mercury is less than 10° above the west-southwest horizon. Saturn and the crescent moon are over 10° to Mercury’s upper left.

While looking for Mercury this morning, look westward toward Jupiter and the bright moon near Gemini.

Jupiter, Moon before Sunrise

Jupiter, Moon, December 7, 2025
Chart Caption – 2025, December 7: Jupiter, moon, and Pollux form a compact bunch in the western sky before sunrise.

One hour before sunrise, the waning gibbous moon, 91% illuminated, is over 40° above the western horizon, 4.7° to Jupiter’s lower right, 6.7° to Castor’s lower left, and 4.4° below Pollux. Jupiter, Moon, and Pollux tightly fit into the same binocular field.

Look for Mercury as it reaches greatest elongation before sunrise. At this hour, Jupiter and the moon are in the western sky.

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