Sky Diary December 2025

Geminid meteors possibly the best of the year, Supermoon, Regulus occultation, Comets, Saturn and Jupiter

by Mark Phillips
Data from Dominic Ford’s in-the-sky.org and other sources

The Geminid meteor shower is the highlight of the month, with peak rates expected to exceed 110 meteors per hour. The Moon will stay well out of the way at maximum, ensuring dark skies. December also brings another “Supermoon,” as the Moon reaches perigee at the same time as the full phase.

On 7 December, the Moon and Jupiter will make a close approach, passing within 3°36′ of each other. The Moon will be 17 days old at the time.

The Winter Solstice occurs on 21 December, marking the shortest day of 2025 in the northern hemisphere.

The Moon occults the brightest star in the constellation of Leo, Regulus on 10 Dec, visible from Edinburgh with the disappearance of Regulus (Alpha Leonis) behind the Moon at 07:16 GMT in the south-western sky at an altitude of 39.1 degrees. Its reappearance will be visible at 08:18 GMT, though in much brighter morning skies.

Both Saturn and Jupiter are prominent in the evening sky with Jupiter becoming more easily accessible in the early evening, bright at mag. -2.6.

The 3rd interstellar object discovered, 3I/ATLAS, is visible in the early morning sky and fading on its way out of our solar system. On 1 Dec it rises at 01:26 GMT and reaches an altitude of 33° above the southern horizon. Watch the recent talk about this fascinating object given by Dr Darryl Z. Seligman.

Comet C/2025 R2 (SWAN) is still easily visibly in the evening skies though getting much fainter now, round about mag. 12. C/2025 K1 (ATLAS) continues to be visible and has now broken up, with three parts that were clearly visible (no longer). It is now circumpolar so visible all night but getting fainter.

Highlights:

• 4 Dec – Full Moon, supermoon, known as the “Cold Moon”
• 7 Dec – The Moon and Jupiter will make a close approach passing within 3°36′ of each other
• 8 Mercury greatest elongation from the Sun in its Nov–Dec 2025 morning apparition. Mag -0.5.
• 10 Dec – The Moon occults Regulus in the morning 07:16 GMT
• 14 Dec- peak of the Geminid meteor shower, active between 4 – 17 Dec, around 110 meteors per hour predicted at peak
• Observe Saturn in the evening, 29° altitude at 19:19 GMT 15 Dec
• Observe Jupiter late night, early morning, maximum 55° altitude around 02:16 GMT 15 Dec, mag -2.6
• 20 Dec – New Moon
• 21 Dec – 15:04 GMT December Winter Solstice
• Interstellar comet 3I/ATLAS visible early morning but fading
• Comet C/2025 R2 (Swan) fading but getting higher in the sky
• Comet C/2025 K1 (ATLAS) has broken up but circumpolar so visible all night