December is an extreme month, cold and dark, but for amateur astronomers and stargazers, it’s also one of the most wonderful months of the year. December 2023 is another busy month for the night sky. The standard (and impressive) meteor shower is complete and a delight. Mercury also shows its fickle nature, with Venus rising in the pre-dawn sky all month long, and her December solstice marking the change of seasons. That means there’s no shortage of reasons to pack up and head out in the cold this month with few clear night skies.
December 3 — The International Space Station (ISS) passes almost overhead.
The extremely bright ISS will be visible until it passes almost overhead, low in the western sky at 4:59 p.m., and disappears low in the eastern sky at 5:06 p.m.
December 4th — third quarter month
During the third (or last) quarter phase at 9:49 pm (local time), the Moon will appear half-illuminated on the sun’s side in the west. It rises around midnight local time and remains visible until it sets in the western daytime sky in the early afternoon. The dark, moonless evening sky that follows this stage is perfect for observing deep-sky objects like the Andromeda Galaxy, which is the brightest in the sky. The Andromeda Galaxy will be directly overhead at 7:30pm (local time).
December 8th — Evening peak of Mercury
Because Mercury is so close to the Sun, it can only be observed when it reaches its “highest” point in the sky, as it is currently visually farthest from the Sun. This occurs regularly as part of Mercury’s 88-day revolution. On December 8, Mercury will be visible just after sunset at 7° above the southwest horizon (just above the horizon). Start looking around 4:10pm (local time). This is a great opportunity to go out and try to find some of the smallest yet extremely bright planets.
December 9th — Venus and Moon conjunction
The two brightest objects of the night, the slender waning crescent moon and Venus, will be only 4 degrees apart in this morning’s predawn sky. Look for Venus in the predawn sky throughout the month.
December 12th — New Moon
The moon is on the same side of the Earth as the sun, so it is not visible in the night sky. This is the best time to observe dark astronomical objects such as galaxies (Andromeda), nebulae (Orion), and star clusters, as the moon’s light will not interfere.
December 13th — Orion Nebula
Now is the perfect time to pull out your binoculars or telescope and observe the Orion Nebula. To the naked eye, this nebula is the center star of the Sword of Orion.
December 14th — Geminid meteor shower peak
Those nights are Dec. 13-15. On the night of the 14th, the Geminid meteor shower will peak at up to 120 meteors per hour, but you likely won’t see that many. This shower is produced by debris left behind by an asteroid known as 3200 Phaethon, which was discovered in 1982. The meteors appear to be coming from the constellation Gemini. Find this constellation in the northern sky using the bright stars Castor and Pollux. Visibility of the meteor will be aided by the new moon, which will be out of the way. This meteor shower is expected to peak around sunset on the 14th, and meteors may be seen on the night of December 13th and 14th.
December 19th — crescent moon
when the moon completes the first quarter of its journey around Earth at 10:39 a.m. (local time). Due to its 90 degree angle away from the Sun, the eastern side of the Moon appears to be half illuminated.
The crescent moon always rises around noon and sets around midnight, so it can be seen in the daytime sky in the afternoon. The evening hours surrounding the first quarter are ideal for viewing the moon’s topography, as it is dramatically illuminated by low-angle sunlight, especially along the terminators (the pole-to-pole boundaries that separate light from the darker hemisphere).
December 21st — winter solstice
For those of us living in the northern hemisphere, December 21st marks the winter solstice. For those of us who love the night sky, this day is not only the shortest day of the year, but also the longest night. A total of 15 hours and 36 minutes, including 11 hours and 50 minutes of darkness. Unfortunately, it’s very cold outside. I’ll tie it up!
December 21st and 22nd — Moon and Jupiter conjunction
The crescent Moon will shine at 5° to the right of Jupiter at 8 pm (local time) on December 21st, and 7° to the left of Jupiter just after sunset on December 22nd. This is a great time to take note of how bright our moon is. It travels through the sky, orbiting the earth within 24 hours.
December 26th — Full moon.
The moon will be on the opposite side of the Earth from the sun, and its side will be fully illuminated. This phase occurs at 4:33 PM local time. This full moon was known as the Cold Moon by early Native American tribes. The reason is obvious. This moon is also known as the Long Nights Moon and the Moon Before Yule (but not this one).
John Taylor is an amateur astronomer who lives in Hayden.