December Moon & Planet data for 2013

The Solar System in December 2013

All dates and times are NZDT (UT + 13 hours) unless otherwise specified.

Phases of the Moon (times as shown by guide)

New moon:      December  3 at  1.23 pm (00:23 UT)
First quarter: December 10 at  4.12 am (Dec 9, 15:12 UT)
Full moon:     December 17 at 10.28 pm (09:28 UT)
Last quarter   December 26 at  2.48 am (Dec 25, 13:48 UT)

The southern hemisphere summer solstice is on December 22 at 6:12 am (December 21, 17:12 UT).

The Planets in December

Venus starts December high and prominent in the evening sky, but will steadily lose altitude during the month as it moves towards conjunction early in 2014. Jupiter will become visible in the late evening.

Jupiter will also be visible in the morning sky, while Mars will rise some hours before the Sun. Saturn will emerge out of twilight during December, but Mercury will be too low in the dawn sky to see.

VENUS, the evening planet.

December sees the virtual disappearance of Venus from the evening sky. At first it sets more than 3 hours after the Sun, just after midnight (NZDT) for much of New Zealand. In the early part of the month it will remain readily visible quite high to the west shortly after sunset. As the month progresses the planet’s elongation from the Sun rapidly declines so it will get lower in the sky and set earlier, so that by the end of December it will set less than an hour after the Sun.

At the beginning of December Venus will be some 30% sunlit as seen from the Earth. During the month as it catches up with the Earth in it orbit, the amount lit will drop to little more than 4%, so the planet will look like a very thin, brilliant, crescent moon as seen through a small telescope. Its distance from the Earth drops from 66 to 42 million km during December and the apparent size of the disc increases correspondingly. As a result the brightness of the planet scarcely changes.

JUPITER will be visible for much of the night by the end of December, rather low to the northeast in the evening. It rises shortly before midnight in New Zealand at the beginning of the month, but gets steadily earlier to rise only a few minutes after sunset by the 31st. From New Zealand the planet will remain a low object due to it being well north of the celestial equator.

Jupiter is in Gemini throughout December moving slowly in a retrograde sense towards the west. It will be a few degrees from Pollux, the brightest star of the constellation. The fainter star delta Gem, magnitude 3.5, will be much closer to Jupiter, with the two only 15 arc-minutes apart, half the diameter of the full moon, on the 10th.

The moon, just past full, will be about 5° from Jupiter on the evening of the 19th.

The morning sky.

MARS moves higher into the morning sky during December. It rises about 3 hours before the Sun on the 1st and four and a half hours earlier by the 31st. The planet is close to the celestial equator so will get higher than Jupiter. It brightens slightly during the month from magnitude 1.2 to 0.9.

Mars is in Virgo throughout December and will move in the direction of Spica, the brightest star in the constellation. The moon, at last quarter, will be just over 5° from Mars on the morning of December 26.

SATURN moves out from the Sun into the morning sky during the month. It rises about 1 hour before the Sun on the 1st and 3 hours before it on the 31st. At first in December it will be low and difficult to see. By the end of December the planet will be readily visible before dawn about 20° above the horizon to the east.

Saturn is in Libra all month. At the end of December it will be almost equi-distant from the two brightest stars in Libra. The crescent moon will be a degree from alpha Lib and just under 5° from Saturn on the morning of the 29th.

MERCURY rises little more than half an hour before the Sun early in the month, making it virtually impossible to see. It closes in on the Sun during the following 4 weeks to be at superior conjunction at the far side of the Sun on the 29th.

Outer Planets

Both Uranus and Neptune are principally evening objects during December. Uranus at magnitude 5.8 is stationary on the 18th and spends the month on the border of between Pisces and Cetus. It sets well after midnight, about 3.30 am on the 1st and 1.30 am on the 31st.

Neptune is at magnitude 7.9 and is in Aquarius. It sets about 90 minutes before Uranus.

Brighter Asteroids:

(1) Ceres and (4) Vesta are both morning objects in Virgo a few degrees from one another and a few degrees from Mars. The three form a rough line with Vesta in the middle. Ceres will be to the lower right of Vesta and Mars to its upper left. The two asteroids are 6° apart at the beginning of December, 5° at the end of the month, when Vesta will also be 8° from Mars.

Ceres is at magnitude 8.7 to 8.6 during December while Vesta brightens a little more from 8.0 to 7.7. Both will be readily visible in binoculars, their changing position compared to the stars visible from night to night.

(2) Pallas is in Hydra and brightens during December from 8.5 to 8.0 so similar in brightness to Ceres and Vesta. It rises just before 11 pm at the beginning of December and about 9.30 pm by the month’s end.

The follwing table lists various solar system object events during December. A list of astronomical terms used in may be found after the table.

December 1 Saturn 1.2 degrees north of the Moon Occn
Mercury 0.5 degrees south of the Moon Occn
December 3 Moon new
Moon southern most declination (-19.6 degrees)
December 4 Moon at perigee
Pluto 1.8 degrees south of the Moon
December 8 Neptune 5.3 degrees south of the Moon
December 9 Moon first quarter
December 11 Uranus 3.1 degrees south of the Moon
Mercury 4.6 degrees north of Antares
December 16 Aldebaran 2.6 degrees south of the Moon
December 17 Moon northern most declination (19.6 degrees)
Moon full
December 18 Uranus stationary
December 19 Jupiter 4.9 degrees north of the Moon
Moon at apogee
December 20 Venus stationary
December 21 Solstice
December 22 Regulus 5.1 degrees north of the Moon
December 25 Moon last quarter
Mars 4.4 degrees north of the Moon
December 27 Spica 1.1 degrees south of the Moon Occn
December 29 Saturn 0.8 degrees north of the Moon Occn
Mercury superior conjunction
December 31 Moon southern most declination (-19.5 degrees)
Mercury 4.6 degrees south of Pluto
  • apogee: Furtherest point in the orbit of a body orbiting the Earth
  • declination: 'Latitude' for celestial objects. The distance in degress above (north) or below (south) the celestial equator.
  • perigee: Nearest point in the orbit of a body orbiting the Earth
  • superior conjunction: Conjunction where the Sun is between the Earth another solar system object