Royal Astronomical Society of New Zealand

The Evening Sky in December

Download a PDF containing this chart, additional charts for specific areas of the sky and descriptions of interesting objects visible at this time of year.

All five of the naked-eye planets are in the early evening sky, but some are easier to find than others. Venus and Mercury are low in the southwest. At the beginning of the month brilliant Venus sets 40 minutes after the Sun. Mercury is then above Venus but may be hard to see in the twilight. By mid-month Venus is setting an hour after the Sun. Mercury, above and right of Venus, sets 30 minutes later. Mercury sinks back into the twilight as it moves between us and the Sun.  On the 28th it will be just to the right of Venus but may be too faint to see by eye in the twilight.

Saturn, Jupiter and Mars are spaced across the evening sky.  Jupiter is the brightest ‘star’ in the sky after Venus sets, shining in the northwest with a steady golden light.  Saturn is due west, well below and left of Jupiter.  It is the brightest ‘star’ in an empty region of sky.  Mars is the brightest orange-red ‘star’ in the northeast.  Nearby are orange stars Aldebaran and Betelgeuse. Mars is at its closest distance for this year on the 8th, 82 million km away. It is still small in a telescope.  At 100x magnification it looks as big as the full moon does to the naked eye. The Moon will appear close to Jupiter on the 2nd and again on the 29th. It is near Mars on the 8th. The Moon is below Saturn on the 26th and above it on the 27th.  

The brightest true stars are in the east and south.  Sirius, the brightest star, but fainter than Jupiter and Mars, is due east at dusk, often twinkling like a diamond.  Left of it is the bright constellation of Orion. The line of three stars makes Orion's belt in the classical constellation. To southern hemisphere sky watchers they make the bottom of 'The Pot'.  The faint line of stars above the bright three is the Pot's handle or Orion's sword. At its centre is the Orion Nebula, a glowing gas cloud nicely seen in binoculars.  Rigel, directly above the line of three stars, is a hot blue-giant star.  Orange Betelgeuse, below the line of three, is a cooler red-giant star.

Left of Orion is a triangular group making the upside-down face of Taurus the bull. Aldebaran, at one tip of the V shape, is one eye of Taurus.  The stars on and around the V, except for Aldebaran, are the Hyades cluster. Aldebaran is not a member of the cluster but on the line-of-sight.  Further left is the Pleiades/Matariki/Subaru cluster, a tight grouping of six naked-eye stars.

Canopus, the second brightest star, is high in the southeast.  Low in the south are the Pointers, Beta and Alpha Centauri, and Crux the Southern Cross upside down at this time of the year. In some Maori star lore the bright southern Milky Way makes the canoe of Maui with Crux being the canoe's anchor hanging off the side. In this depiction the Scorpion's tail, just setting, can be the canoe's prow and the Clouds of Magellan are the sails.

The Milky Way is wrapped around the horizon. The broadest part is in Sagittarius, low in the southwest around Venus.  It narrows toward Crux in the south and becomes faint in the east below Orion. The Milky Way is our edgewise view of the Galaxy. The Galaxy’s thick hub or central bulge is 27 000 light-years away, in Sagittarius.  The nearby outer edge is the faint part of the Milky Way below Orion.  

The Clouds of Magellan, LMC and SMC, high in the southern sky, are two small galaxies about 160 000 and 200 000 light-years away, respectively.  They are easily seen by eye on a dark moonless night as misty patches of light.

Very low in the north is the Andromeda Galaxy. In binoculars in a dark sky it looks like a spindle of light.  It is a bit bigger than our Milky Way Galaxy and nearly three million light-years away.

*A light-year (l.y.) is the distance that light travels in one year: nearly 10 million million km. Sunlight takes eight minutes to get here; moonlight about one second. Sunlight reaches Neptune, the outermost major planet, in four hours. It takes sunlight four years to reach the nearest star, Alpha Centauri.

Notes by Alan Gilmore,
University of Canterbury's Mt John Observatory, 
P.O. Box 56, 
Lake Tekapo 7945,
New Zealand.