December begins with the moon just ending her final phases - four days from new moon Dec. 5.
Then, Dec. 6 and 7, our satellite brushes past first Mars and then Mercury, both planets dimly seen in the west right after sunset, accompanied by a very thin slice of moon - a challenging pair of observations.
By Dec. 19, the moon has moved eastward in its orbit enough to be among the many stars of the Pleiades (Seven Sisters). Dec. 21 is full moon and a total lunar eclipse especially well placed for viewers in North America. Unfortunately, the eclipse occurs mostly after midnight Dec. 21 and lasts for several hours. It represents considerable dedication to stay up to watch the show. Nevertheless, first contact is at 11:29 p.m. Dec. 20, when the moon enters Earth's penumbral shadow. Total eclipse lasts from 1:40 to 2:53 a.m.; the final stages of penumbral eclipse last until 5:04. During the eclipse, the star cluster M35 will be just above the moon, and should be visible during the total stage of darkness. Later that day the solstice marks the official beginning of winter.
Mercury is as far from the sun as it can be at the beginning of December, then gradually it rounds in front of the sun, making a difficult observation, at best. The shallow angle of the ecliptic means that viewers require a clear, unobstructed western horizon and good eyesight to see this fleetest of planets.
Venus is a "Morning Star" all through December, rising in the southeast around 5 a.m., a beacon gracing the early morning sky. The moon shares the sky with Venus on the morning of Dec. 2.
Mars is in much the same position as Mercury, but moving much more slowly. It's still a difficult sighting, as it competes with the sun's glare in the early evening, slipping below the horizon as twilight arrives.
Jupiter never fails to please and right now is a great time to see the giant plant and its moons. Dec. 14, the moon is within seven degrees of Jupiter.
Uranus is close to Jupiter all through the month, a bit too far away to be mistaken for one of the Galilean moons - a greenish orb to the northeast of Jupiter.
Neptune is about 15 degrees to the west of the Jupiter/Uranus pair. Neptune sets about 9:30 p.m., while Jupiter/Uranus set at midnight.
The morning of Dec. 14 is the time to watch for the annual spectacle of the Geminid meteor shower, predicted to be about 120 meteors per hour under the best viewing conditions.
- James Edgar has had an interest in the night sky all his life. He joined The Royal Astronomical Society of Canada in 2000. He is editor's assistant and a contributor to the Observer's Handbook, Production Manager of the bi-monthly RASC Journal, and is the society's national secretary.
