December Skies

- James Edgar

December 10, 2024

Key points from this story:

• New Moon on December 1 and 30
• Venus prominent in western evening twilight
• Mars begins retrograde motion on December 7
• Jupiter well-placed for evening viewing in Taurus
• Winter solstice on December 21 morning
• Geminid and Ursid meteor showers peak

The Moon is new on December 1. By the 4th, the Moon’s thin sliver in the west is joined by Venus, just 2 degrees to the north. On the 8th, Saturn is a mere 0.3 degrees south of our first-quarter satellite, occulted for viewers in the Southern Hemisphere. The Moon is at perigee (closest to Earth) on the 12th at 365,361 km. On the 13th, with the waxing gibbous Moon among the stars of the Pleiades, Uranus is 4 degrees south. Jupiter is 5 degrees south of the Moon on the 15th, which will be full on the 16th. Might be a good time for a photo opportunity. The 18th sees the Moon occulting Mars for observers in the extreme north of Canada—otherwise a close conjunction of less than a degree. On the 24th, the Moon is at apogee (farthest from Earth) at a distance of 404,485 km. That evening sees Spica hugging Luna at only 0.2 degrees away. Spica is the bright star in Virgo, The Maiden. The 28th has the red star Antares just 0.09 degrees north of the Moon, an occultation in the Southern Hemisphere. And, finally, 29 days later, the Moon is new again on the 30th.

Mercury is too close to the Sun for safe viewing during the first half of December. It rises in the early morning eastern sky, skirting north of Antares on the 22nd. Venus is prominent in the western evening twilight and joined by the Moon on the 4th. Each passing day sees the brightest planet rise higher and higher. Mars is among the stars of Cancer, The Crab, rising just a half hour after Orion to the west. The Red Planet begins retrograde motion on the 7th, seemingly moving westward (but it’s the Earth moving faster that causes this strange behavior). The planet is well placed for evening viewing, with Pollux and Castor a bit north, Orion to the west, and Jupiter high above.

Jupiter is well placed for evening viewing among the stars of Taurus, The Bull. The Moon is 5 degrees north on the 15th. Saturn rises in early afternoon, making an appearance at sundown, a little to the northeast of Venus. The Ringed Planet is approaching a ring crossing in March 2025, so the rings gradually become edge-on. Unfortunately, the ring crossing occurs when Saturn is hidden by the Sun, so a non-event. Uranus rises in the late afternoon ahead of Jupiter. The Pleiades are easy to spot just to the northwest of Jupiter, so the blue-green Uranus may be picked out of the starry background. It’s the spot that doesn’t twinkle.

Neptune, the elusive planet. It’s so far away that it looks impossibly small. You’d have to use powerful binoculars or a medium powered telescope to see it, and even then it’s a tiny spot. The blue planet is among the stars of Pisces, The Fish.

Winter solstice is on the early morning of December 21. The Geminid meteors peak on the evening of the 13th. The Ursid meteors peak on the morning of the 22nd.