December will be an interesting month in the sky. Saturn will start the month almost straight south during the early evening in a dim part of the sky. The only reasonable bright stars nearby are the Great Square of Pegasus (the Winged Horse) about two fist-widths above Saturn. During the month, Saturn will start to drift into the southwestern sky as Earth in its faster orbit starts to leave it behind. Very bright Jupiter will join Saturn after it rises at about 8:00 as December begins and at about 6:00 by the end of the month. It will be to the lower right of Pollux and Castor, above Pollux, the bright twin stars of Gemini (the Twins).

The other planets will be more of a challenge to see. Mars technically will be in the southwestern evening sky during early December, but it will set within a half hour after the Sun. It will probably not be visible without binoculars and a very clear western horizon. Venus also may be difficult to spot. It will shine very low in the southeast just before sunrise. Mercury will rise before Venus and should be easier to see. Although this is Mercury’s best morning appearance for the year, it will still be low in the southeastern sky.

This is also the time of the year when Cassiopeia (the Queen) is at her highest in the northern sky. Look almost overhead for the unmistakable “E” or “M” formed by Cassiopeia’s five moderately bright stars. The bottom or open part of the grouping points toward Polaris, the North Star, the only moderately bright star in that part of the sky. This is useful in finding north at this time of the year when the Big Dipper, which is usually used to find north, is very low in the sky and is often obscured.

If the stars of Cassiopeia are numbered with the western-most star being 1, they can be used to find other constellations. A line from star 2 through star 1 points a short distance to Cepheus (the King). His five brightest, but dim, stars form the shape of a stick house with its pointed roof near Polaris. A line from star 3 through star 4 points to Perseus (the Hero) and midway the dim Double Cluster. A line from star 3 through star 2 points farther to the Great Square of Pegasus (the Winged Horse). The northeastern star of the Great Square is also a part of Andromeda (the Princes). Her brightest stars extend eastward as a line of two more stars. Finally, stars 1, 2, and 3 form an arrow that points to the Andromeda galaxy that is visible with binoculars.

These constellations are the main characters in a story from Greek mythology. Cassiopeia was beautiful, but when she boasted that she was more beautiful than the sea nymphs (minor goddesses), Poseidon (Roman, Neptune) did not like it. To punish her, he sent Cetus (the Sea Monster) to ravage the coast. In order to find a way to stop this, Cassiopeia and her husband Cepheus consulted an oracle who gave them the distressing news that the only way to stop the sea monster was to sacrifice their daughter Andromeda to it. They reluctantly did this by chaining Andromeda to a rock along the coast. At the last minute, Perseus came flying by on the winged sandals that he had been given by Mercury and accompanied by Pegasus. Perseus was returning from killing the Gorgon Medusa, who would turn anyone to stone that looked at her. Perseus carried her head in a bag, but he exposed the head and turned the sea monster to stone, saving Andromeda. They later flew off together on Pegasus.

Observing Highlights

-Dec. 4: The Moon will be to the upper left of Aldebaran, the brightest star in Taurus (the Bull).

-Dec. 6: After they rise at about 8:00, the Moon will be above very bright Jupiter and to the right of Castor and upper right of Pollux, the bright twin stars of Gemini (the Twins).

-Dec. 7: Mercury will be at its highest point above the eastern horizon. Look about 45 minutes before sunrise. Mercury will be about as high for a few mornings before and after this date.

-Dec. 13: The Geminid meteor shower will peak tonight with meteors seeming to have come from near the bright star Castor in Gemini (the Twins). This shower has the advantage that the peak comes early, so many meteors can be seen before midnight. Up to 100 meteors an hour may be seen under optimal conditions.

-Dec. 17: The crescent Moon will be to the upper right of Mercury, quite low in the sky during morning twilight.

-Dec. 21: The day of the winter solstice, which marks the longest night of star gazing for the year.