December Skies – by Dick Cookman

Highlights:  Comet Journal, Martian Landers, Meteor Showers, December Solstice, Planet Plotting, December Moon

Focus Constellations: Ursa Minor, Ursa Major, Draco, Cygnus, Cepheus, Cassiopeia, Perseus, Camelopardalis, Gemini, Auriga, Taurus, Perseus, Andromeda, Pegasus, Pisces, Aries

  • Comet Journals

Comet 67P/Churyumov-Gerasimenko (2021) is in Cancer at 8th magnitude in December. It was at perihelion on November 3 and was closest to Earth on November 12.

C/2021 A1 (Leonard) is a long period (80,000 years) comet. It will be closest to Earth on December 12, and at perihelion on January 3, 2022. It is currently approaching 8th magnitude in Canes Venatici and is expected to move through the northern hemisphere night sky to Aquarius by month’s end and get much brighter in the 1st two weeks of December when it may become visible to the naked eye! Find it in the SE dawn sky until the 12th and low in the SW dusk sky afterwards.

Comet 4P/Faye is in Monoceras at 10th magnitude in December. Faye passed perihelion on September 8 and will be closest to Earth on December 6.

Comet 6P/d’Arrest (2021) moves through southeastern Aquarius and may reach magnitude 9 in December. It was closest to Earth in August and passed perihelion on September 17.

  • Mars Landers

After stowing its newly acquired drill cores, Perseverance Rover wrapped up operations at Citadelle in Jezero Crater on Sept. 21 and headed into South Seitah, a level area which may be an ancient lake bed in the crater. It wended its way between and around sand dunes and sand traps on a course scouted by Ingenuity helicopter. The rover evaluated a drill site at the Brac rock outcrop and extracted a core sample in mid November.

InSight Lander’s seismometer measured seismic waves from crustal vibrations induced by wind to develop a model describing fine structure of the bedrock in Elysium Planitia. Below an upper sandy layer 3 meters thick a 15 meter thick layer of coarse, blocky impact ejecta rests on a 150 meter thick layer of interbedded sedimentary material and volcanic lava flows.

After the solar conjunction last month, Curiosity Rover crushed and evaluated some nodules found in late September and headed to Siccar Point, a promontory with a major geologic unconformity where much younger rock layers overlie very old layers. The surface between represents a long episode of erosion which removed the layers formed during the interval. South of the point, the approach to the escarpment of the prominent flat-topped Greenheugh Pediment which dominates the western horizon was chosen for the 40th drilling target called Zechstein. Drilling was successfully completed on November 8 (Sol 3292), and the balance of November was spent processing and analyzing the drilling sample.

  • Meteor Showers

The Geminids join minor December Meteor showers including the Chi Orionids, Sigma Hydrids, Coma Berenicids, and Ursids. The Ursids can sporadically storm and the Geminids are one of the best meteor showers of the year.

December 2: Chi Orionids/December 12: Sigma Hydrids – less than 5 meteors/Hr in dark skies without stray light

December 14: Geminids. Active Dec. 7 – 17. Radiant 7h28m +33°. ZHR 120. 35 km/sec. Waxing Gibbous Moon. Progenitor: Asteroid (3200) Phaethon. 

December 20: Coma Berenicids. Active Dec. 12-Jan. 23. Radiant 11h40m +25°. ZHR 5. 65 km/sec. Waning Gibbous Moon. Progenitor: Comet Lowe.

December 22: Ursids. Active Dec. 17 – 26. Radiant 14h28m +76°. ZHR up to 50+. 33 km/sec. Waning Gibbous Moon. Progenitor: Comet 8P/Tuttle.

  • December Solstice

The solstice is on the 21st at 10:59 AM EST. The longest night of the year will be followed by the shortest day.

  • Planet Plotting

Mars (1.6 to 1.5) is December’s morning planet. It rises almost two hours before the Sun and brightens slightly during the month as it moves from Libra to Ophiuchus and Earth starts to close in on the orbiting red planet. 

Venus (-4.3 to -4.9 to -4.5) in Sagittarius is at its brightest on the 4th when it blazes out of the southwestern sunset twilight. Mercury will join Venus in late December when it climbs into twilight after its Superior Conjunction with the Sun in late November. The two will pass within 4 degrees of each other on the 28th as Venus falls deep into twilight, approaching Inferior Conjunction with the Sun in early January. Saturn (+0.7) in Capricornus and Jupiter (-2.1 to -2.0) in Capricornus and Aquarius rise in the eastern sky before noon and are best viewed in the early evening when highest in the southwestern sky. They set in the mid to late evening. Neptune (+7.9) rises in early afternoon in Aquarius and Uranus (+5.7) in Aries rises about 3 hours later.

Planet Constellation(s) Magnitude Planet Passages Time Date
Sun Libra – Scorpius -26.5 New Moon 2:43AM EST 12/4
Mercury Ophiuchus – Sagittarius -1.1 to -0.7 Venus, 4.0°N 8:00PM EST  12/28
Venus Sagittarius -4.5 to -4.2 Mercury, 4.0°S 8:00PM EST 12/28
Mars Libra – Ophiuchus +1.6 to +1.5
Jupiter Capricornus – Aquarius -2.1 to -2.0
Saturn Capricornus 0.7
Uranus Aries 5.7
Neptune Aquarius 7.9
  • December Moon

The New Moon of December on the 4th at 2:43AM EST is the start of Lunation 1224 which ends 29.45 days later with the New Moon of January 2 at 1:33PM EST. The Full Moon of December is on the 18th at 11:35PM EST. December’s Moon is called ”Cold Moon,” “Moon before Yule,” or “Long Night Moon”. The latter refers to the fact that the Full Moon is above the horizon for a longer time than at any other time of the year due to the high arc that it takes through the sky as the Earth rotates. For northern hemisphere observers, the Full Moon is highest in the sky in December and the Sun is lowest because Earth is tilted away from the Sun and toward the Full Moon. In colonial America it was the “Christmas Moon” and was named the “Oak Moon” in Medieval England. Celts called it “Wolf or Bitter Moon” and the Chinese call it “Bitter Moon”.

Of the 13 Grandmother Moons during each year, Anishnaabe (Odawa and Ojibwe) people of northern Michigan call it “Manidoo-gizisoons” (Little Spirit Moon.) The associated cultural teaching that explains the cycle of life and nature for the 12th Moon is: “a time of healing. By receiving both vision of the spirits and good health, we may walk the Red Road with purest intentions, and we can share this most positive energy with our families and friends for the good of all.”

Lunar Perigee distance (minimum lunar distance) is 221,702 mi. (55.94 Earth radii) on the 4th at 5:04AM EST. Lunar Apogee (maximum lunar distance) is on December 17 at 9:15PM EST, when the Moon will be at a distance of 252,475 mi. (63.70 Earth radii).

The waning crescent Moon will appear to pass the morning planet, Mars, on the 2nd and 31st. The waxing crescent Moon appears to pass the evening planets: Mercury on the 4th, Venus on the 6th, Saturn on the 7th, Jupiter on the 9th, and Neptune on the 10th. The waxing gibbous Moon will appear to pass Uranus on the 15th. 

Planet Constellation Magnitude Moon Passages Moon Phase Moon Age
Sun Ophiuchus -26.8 2:43AM EST, 12/4 New 0 Days
Mercury Ophiuchus -1.0 0.42° ESE, 11:00AM EST, 12/4 Waxing Crescent 0.35 Days
Venus Sagittarius -4.6 1.9°S, 8:00PM EST, 12/6 Waxing Crescent 2.72 Days
Mars Libra 1.6 0.7°N, 7:00PM EST, 12/2 Waning Crescent 27.57 Days
Mars Ophiuchus 1.5 0.9°N, 3:00PM EST, 12/31 Waning Crescent 27.52 Days
Jupiter Capricornus -2.1 4.0°S, 1:00AM EST, 12/9 Waxing Crescent 4.93 Days
Saturn Capricornus 0.7 4.0°S, 9:00PM EST, 12/7 Waxing Crescent 3.76 Days
Uranus Aries 5.7 1.5°S, 1:00AM EST, 12/15 Waxing Gibbous 10.93 Days
Neptune Aquarius 5.7 4.0° S, 8:00PM EST, 12/10 Waxing Crescent 6.72 Days