December Skies by Dick Cookman
Highlights: Comet Journal, Martian Landers, Meteor Showers, Planet Plotting, December Moon
Focus Constellations: Ursa Major, Ursa Minor, Draco, Cygnus, Cepheus, Cassiopeia, Camelopardalis, Lynx, Gemini, Auriga, Perseus, Andromeda, Pegasus, Pisces, Aries, Taurus
Comet Journals
Comet C/2021 S3 (Panstarrs) is a long period comet orbiting through Centaurus in southern hemisphere skies and will move northward in late winter (just like some people I know). It will reach perihelion on February 14, 2024 at about 7th magnitude and will be brightest on March 1 in Serpens Cauda. It passes perigee (closest to Earth) on March 14 then heads back home as in leaves the Solar System.
Comet 62P/Tsuchinsham 1 2023, a short period (6.67 years) comet at 9th magnitude in Leo, may reach 7th magnitude at perihelion on Christmas. After moving into Virgo in January, it will be closest to Earth on the 30th.
Mars Landers
In the October 18th Smithsonian magazine, Shi En Kim summarized current understanding of Martian magnetic fields as follows: “From their high perches above Martian ground, the MAVEN and Mars Global Surveyor satellites confirmed that Mars has no planetary magnetic dipole like Earth. However, mapping revealed pockets of regional magnetic fields stamped all over the crust. The magnetic mosaic comes from volcanic rocks at the surface that carry traces of Mars’s remnant magnetic field.
A planet’s magnetic shield comes from the churning of the sphere’s interior. Melt in the core consisting of swirling iron and nickel generates an electric current, which in turn powers a planet-sized electromagnet. Invisible magnetic field lines envelop most planets in the solar system, including Earth. Being a smaller planet, Mars cooled off much sooner than Earth did, and its roiling innards quietened. With that went Mars’s global magnetosphere. But metals near the planet’s surface captured a snapshot of the field as they solidified, and they have retained their magnetic imprint.
These scattered magnetic fields on the crust lead to spectacular auroras that look nothing like Earth’s. Auroras are caused by charged particles that rain down from the sun into the atmosphere. On Earth, these ghostly glows congregate at the poles, as the magnetic field is strongest there. But the auroras on Mars can shimmy close to the equator, since no planetary field confines them. Photographs taken by the United Arab Emirates’ Hope orbiter in 2021 show that the heavenly displays can take on all kinds of serpentine shapes.”
Meteor Showers
December northern hemisphere meteor showers are the Chi Orionids, Geminids, Coma Berenicids, and the Ursids. The Chi Orionids, Coma Berenicids, and Ursids are minor showers contending with a bright gibbous Moon. The Geminid shower is one of the very best in 2023 and has no competition from the 2 day old Moon. Best viewing is after midnight, the peak hour of 2:00 AM EST, and before dawn when Earth orbits head first into the river of comet debris.
December 14, 2-4AM: Geminids. Active Dec. 7 – 17. Radiant 7h28m +33°. ZHR up to 120. 35 km/sec. Favorable, Waxing Crescent Moon. Progenitor: asteroid known as 3200 Phaethon
December 22, 4AM: Ursids. Active Dec. 17 – 26. Radiant 14h28m +76°. ZHR 5-50. 33 km/sec. Unfavorable – Waxing Gibbous Moon. Progenitor: Comet 8P/Tuttle.
Planet Plottings
In early December, Venus (-4.2 to -4.1) is a morning planet rising about 4:00AM. Virgo’s 1st magnitude star, blue giant Spica, is above and south of Venus. Arcturus in Bootes is the bright star above and north. On the 11th, Venus moves from Virgo into Libra. The separation between Spica in Virgo and Venus increases throughout December as the planet appears to approach the red supergiant Antares in Scorpius.
Mercury (-0.4 to +0.9) in Sagittarius and Ophiuchus is just above the west-southwest horizon after sunset on the 1st. After rising higher each night until reaching greatest eastern elongation of 21 degrees on the 4th, it dims as it descends into the glow of sunset. Saturn (0.9) in Aquarius and Neptune (7.8 to 7.9) in Pisces are also evening planets which are higher in the Southwest and South respectively. The latter sets after midnight. Jupiter (-2.8 to -2.5) and Uranus (5.6 to 5.7) in Aries were at opposition last month and are diminishing in brightness. Jupiter is still an impressive sight in the evening sky and, like Uranus, is visible almost all night long. Mars is not visible in December, solar conjunction was on November 18 and the planet is still lost in the Sun’s glare.
|
Planet |
Constellation(s) |
Magnitude |
Planet Passages |
Time |
Date |
| Sun | Libra, Scorpius |
-26.5 |
New Moon |
6:32PM EST |
12/12 |
| Mercury | Sagittarius, Ophiuchus |
-0.4 to +0.9 |
Inferior Conjunction |
9:00AM EST |
12/4 |
| Venus | Virgo, Libra |
-4.1 to -4.0 |
|||
| Mars | Scorpius, Ophiuchus |
1.4 |
|||
| Jupiter | Aries |
-2.8 to -2.5 |
|||
| Saturn | Aquarius |
0.9 |
|||
| Uranus | Aries |
5.6 to 5.7 |
|||
| Neptune | Pisces |
7.8 to 7.9 |
- December Moon
December’s New Moon is in Scorpius on the 12th at 6:32PM EST. The New Moon marks the start of Lunation 1249 which ends 29.59 days later with the New Moon of January in Sagittarius on the 11th at 6:58AM EST.
The Full Moon on the 26th occurs at 7:33PM EST in Gemini, five days after the Winter Solstice at 10:27PM EST on the 21st. It is called the Moon before Yule. It was called the Oak Moon in Medieval England. For Celts, it was the Cold Moon and, in China, it is the Bitter Moon. Colonial Americans called it the Christmas Moon.
Anishnaabe (Odawa and Ojibwe) first people respectively recognize the 12th Moon of the year as “Manidoo-Giizisoons” (Little Spirit Moon). Ontario’s Earth Haven Farm presents cultural teachings explaining the cycle of life and nature of the twelfth moon of Creation as the Little Spirit Moon, 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 Apogee (maximum lunar distance) is on December 4 at 1:42PM EST when the Moon’s distance is 251,249 mi. (63.40 Earth radii). Lunar perigee (minimum lunar distance) is on the 16th when the Moon is at 228,603 mi. (57.68 Earth radii) at 1:53PM EST.
The waning crescent Moon appears to pass Venus on the 9th and Mars on the 12th. The waxing crescent passes Mercury on the 13th, Saturn on the 17th, and Neptune on the 19th. The waxing gibbous Moon passes Jupiter on the 22nd, and Uranus on the 23rd, two days after the December solstice (12/21, 10:27PM EST).
|
Planet |
Constellation |
Magnitude |
Moon Passages |
Moon Phase |
Moon Age |
| Sun | Ophiuchus |
-26.8 |
6:31PM EST, 12/12 | New | 0 Days |
| Mercury | Sagittarius |
0.6 |
4.0°S, Midnight EST, 12/13 | Waxing Crescent | 0.61 Days |
| Venus | Virgo |
-4.0 |
4.0°S, Noon EST, 12/9 | Waning Crescent | 26.31 Days |
| Mars | Ophiuchus |
1.4 |
3.5°S, 5:00AM EST, 12/12 | Waning Crescent | 29.52 Days |
| Jupiter | Aries |
-2.5 |
3.0°N, 9:00AM EST, 12/22 | Waxing Gibbous | 9.60 Days |
| Saturn | Aquarius |
0.9 |
2.0°S, 5:00PM EST, 12/17 | Waxing Crescent | 4.94 Days |
| Uranus | Aries |
5.7 |
3.0°N, 10:00AM EST, 12/23 | Waxing Gibbous | 10.65 Days |
| Neptune | Pisces |
7.9 |
1.3° S, 8:00AM EST, 12/19 | Waxing Crescent | 8.56 Days |
