January Moon & Planet data for 2013

The Earth is at perihelion on January 2, when the distance between Earth and Sun will be 0.983 Au, just over 147 million km. The Sun´s apparent diameter will be at its greatest, 32.5 arc-minutes.

Jupiter will be the prominent planet of the evening sky, as will be Saturn in the early dawn sky. Venus will appear low to the east shortly before sunrise. Mars, in the evening, will be very low and become lost in twilight during the month. Mercury starts the month in the morning sky but becomes an evening object after superior conjunction. It is likely to be too close to the Sun to see throughout January.

Mars and Jupiter in The Evening Sky.

Mars sets about 90 minutes after the Sun at the beginning of the year. On the 1st it will be only some 6° above the horizon 45 minutes after sunset. At magnitude 1.2 it will not be an easy object in the still bright sky low to the west. It will get steadily lower during the month so lost to view. By the end of January the planet will be setting about 50 minutes later than the Sun.

Jupiter will be a much easier object. It transits late evening at the beginning of January. At this time the star Aldebaran will be just over 5° to the upper right of the planet. The asteroid Vesta at magnitude 6.9 will be a similar distance also to the right of Jupiter and about half the distance low and slightly to the right of Aldebaran.

Jupiter will be moving in a retrograde sense to the west through January but gradually slowing until in the early hours of the 31st it is stationary. By the 31st the planet will transit and be highest just before 9 pm. Jupiter is currently well north of the equator so low in southern skies. The transit altitude is 28° at Wellington.

On January 22 the moon will occult Jupiter, but before it rises in New Zealand. The event is visible at night in central South America. By the time Jupiter rises in NZ in the afternoon, the moon will be 1° beyond the planet, the distance increasing to 3° by the time the sky is dark.

The Morning Sky: Mercury, Venus and Saturn

Mercury is a morning object for the first part of January. It rises 45 minutes before the Sun on January 1 when it will be 11° to the lower right of Venus, but it will be only 2° up half an hour before sunrise. Observation will thus be very difficult. On subsequent mornings Mercury gets steadily closer to the Sun until it is at superior conjunction on the 18th.

After conjunction Mercury becomes an evening object setting after the Sun. By the end of January it sets only 30 minutes after sunset, so again will be too close to the Sun to observe.

Venus will be a little higher than Mercury in the morning sky and, of course, much easier to see. The planet rises about 80 minutes before the Sun on the 1st and more like 70 minutes earlier by the 31st. Thus it should be fairly easy to see before sunrise, rather low in a direction a little to the south of east.

The thin crescent moon will be some 10° to the upper left of Venus on the morning the 10th. The following morning, as an even finer crescent, it will be only 5° directly below Venus. The strong morning twilight may make the moon difficult to see.

Saturn, in contrast to Mercury and Venus, will be an easy-to-see object before dawn. It rises about 2.30 am NZDT on the 1st and almost 2 hours earlier by the 31st. Saturn will be in Libra moving to the east. An hour before sunrise the planet will be to the left of the double star alpha Lib, the two being less than 5° apart by the end of January.

The crescent moon will be about 5° to the upper left of Saturn on the morning of January 7, and a similar distance to the lower right of alpha Lib the following morning.

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

January 1 Regulus 5.6 degrees north of the Moon
January 2 Earth at perihelion
January 5 Moon last quarter
Spica 0.5 degrees north of the Moon Occn
January 6 Mercury 4.7 degrees south of Pluto
Saturn 3.6 degrees north of the Moon
January 9 Moon southern most declination (-20.8 degrees)
January 10 Moon at perigee
Venus 2.8 degrees south of the Moon
January 11 Pluto 0.3 degrees south of the Moon Occn
Mercury 5.7 degrees south of the Moon
Moon new
January 14 Neptune 5.6 degrees south of the Moon
January 17 Uranus 4.5 degrees south of the Moon
Venus 3.3 degrees south of Pluto
January 18 Mercury superior conjunction
Moon first quarter
January 22 Jupiter 0.5 degrees north of the Moon Occn
Aldebaran 4.0 degrees south of the Moon
Moon at apogee
January 23 Moon northern most declination (20.8 degrees)
January 27 Moon full
January 28 Regulus 5.5 degrees north of the Moon
January 30 Jupiter stationary
  • 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
  • perihelion: Nearest point in the orbit of a body orbiting the Sun
  • superior conjunction: Conjunction where the Sun is between the Earth another solar system object