501.

Conjunction of the Moon and Mercury The Moon and Mercury share the same right ascension, at a separation of 4°21'. Thu, 14 Dec 2023 at 00:20 EDT (195 days ago) in Sagittarius

502.

Geminid meteor shower 2023 The Geminid meteor shower reaches its peak. Thu, 14 Dec 2023 (195 days ago) in Gemini

503.

The Orion Nebula is well placed The Orion Nebula (M42; mag 4.0) culminates at around midnight local time. Fri, 15 Dec 2023 (194 days ago) in Orion

504.

The Running Man cluster is well placed The Running Man cluster NGC 1977 (mag 4.2) in Orion's sword culminates at around midnight local time. Fri, 15 Dec 2023 (194 days ago) in Orion

505.

Comae Berenicid meteor shower 2023 The Comae Berenicid meteor shower reaches its peak. Sat, 16 Dec 2023 (193 days ago) in Leo

506.

The Moon at perigee The Moon makes its monthly closest approach to the Earth, making it appear fractionally larger than at other times of the month. Sat, 16 Dec 2023 at 13:52 EDT (193 days ago) in Capricornus

507.

Conjunction of the Moon and Saturn The Moon and Saturn share the same right ascension, at a separation of 2°28'. Sun, 17 Dec 2023 at 17:01 EDT (192 days ago) in Aquarius

508.

Close approach of the Moon and Saturn The Moon and Saturn pass close to each other. Sun, 17 Dec 2023 at 18:44 EDT (192 days ago) in Aquarius

509.

Lunar occultation of Neptune The Moon will pass in front of Neptune, creating a lunar occultation visible from Australia. Tue, 19 Dec 2023 at 09:16 EDT (190 days ago) in Pisces

510.

Moon at First Quarter The Moon reaches first quarter phase – appearing high in the sky at sunset and setting in the west at around midnight. Tue, 19 Dec 2023 at 13:39 EDT (190 days ago) in Pisces

511.

December Leonis Minorid meteor shower 2023 The December Leonis Minorid meteor shower reaches its peak. Wed, 20 Dec 2023 (189 days ago) in Leo Minor

512.

Mercury at perihelion Mercury passes its orbit's closest point to the Sun. Wed, 20 Dec 2023 at 12:04 EDT (189 days ago) in Sagittarius

513.

Asteroid 4 Vesta at opposition Asteroid 4 Vesta makes closest approach to the Earth. Thu, 21 Dec 2023 at 16:34 EDT (188 days ago) in Orion

514.

December solstice 22 December will be the shortest day of 2023 in the northern hemisphere. Thu, 21 Dec 2023 at 22:24 EDT (188 days ago) in Sagittarius

515.

Close approach of the Moon and Jupiter The Moon and Jupiter pass close to each other. Fri, 22 Dec 2023 at 07:31 EDT (187 days ago) in Aries

516.

Conjunction of the Moon and Jupiter The Moon and Jupiter share the same right ascension, at a separation of 2°36'. Fri, 22 Dec 2023 at 09:24 EDT (187 days ago) in Aries

517.

Mercury at inferior solar conjunction Mercury passes around the near side of the Sun. Fri, 22 Dec 2023 at 13:50 EDT (187 days ago) in Sagittarius

518.

Asteroid 9 Metis at opposition Asteroid 9 Metis makes closest approach to the Earth. Fri, 22 Dec 2023 at 14:10 EDT (187 days ago) in Gemini

519.

Ursid meteor shower 2023 The Ursid meteor shower reaches its peak. Fri, 22 Dec 2023 (186 days ago) in Ursa Minor

520.

Close approach of the Moon and M45 The Moon and M45 pass close to each other. Sun, 24 Dec 2023 at 03:56 EDT (185 days ago) in Taurus