The sky in December and January

On December 1 Mercury rises only an hour and fifteen minutes before the Sun and, at magnitude 1.2, is a bit hard to see. The planet rises earlier each day, however, and soon emerges from the glare of sunrise. By the 5th it is visible low in the east-southeast about forty-five minutes before sunrise, seventeen degrees below and to the left of the much brighter Jupiter. A slender crescent Moon appears to hover about seven degrees to Mercury's right on the morning of the 29th.

On New Year's Day, Mercury rises about an hour before the Sun and shines at magnitude -0.5. A week later, rising just forty-five minutes before the Sun, it is once again hard to see.

In December Venus makes its most magnificent appearance of 2005 and 2006. Look for it in the southwestern sky at sunset. As twilight fades, the planet seems to grow increasingly large and bright; to add to the drama, it pairs with the crescent Moon on the 4th to make an eye-catching sight. Venus reaches its highest altitude of the year early this month, coinciding with the night of its greatest brilliancy, on the 9th. On that night it appears to blaze eighteen degrees above the southwestern horizon forty-five minutes after sunset. By Christmas, Venus is plunging rapidly into the sunset glow.

In early January, Venus vanishes from the evening sky. On the 13th it reaches inferior conjunction, passing more or less directly between the Earth and the Sun. By the 19th Venus emerges as a new morning "star," rising in the east-southeast at mid-dawn. You may be able to spot it about six degrees above the horizon half an hour before sunrise. A week later you should be able to see it easily from any location with an open east-southeastern view, about an hour before sunrise.

Mars begins December shining in the constellation Aries, the ram, in the southeastern sky at dusk, and by 9:30 P.M. it has climbed to its highest point in the sky, due south. At the onset of December Mars shines at magnitude -1.6, but, having faded over the previous few weeks, it is only about half as bright as it was a month earlier. It continues dimming throughout December. Be sure to watch on the night of December 11-12, as the waxing gibbous Moon slowly glides above Mars.

In January the Red Planet shines orange-yellow in the south during early evening. At midmonth it sets in the west at about 2:15 A.M. By month's end it has lost half the brightness it had on the 1st; as a result, it appears about as bright as the bluish-white star Rigel, in the constellation Orion, the hunter. On the evening of the 8th Mars is to the right of a waxing gibbous Moon.

Jupiter is so prominent before sunrise in December that you hardly have to look for it. It's a steady silvery-white lamp that dears the horizon more than two and a half hours before the Sun does at the beginning of the month, and nearly four and a half hours before sunrise as the month ends. At dawn's first light, the gas giant hangs in the southeast. Jupiter is fourteen degrees below and to the left of the bright bluish star Spica, in the constellation Virgo, the virgin, as the month begins. The star and planet then separate as Jupiter drifts eastward. Jupiter appears to ride above and to the right of a crescent Moon on the morning of the 27th.

In January Jupiter continues to be visible before dawn. This month it rises after midnight and is high in the south-southeast by sunup.

Saturn, situated in the constellation Cancer, the crab, begins December rising out of the east-northeast shortly after 9 P.M.; by month's end it's rising two hours earlier. On the evening of the 18th Saturn is below and to the right of the Moon. By the end of December the planet shines brilliantly, even though it doesn't reach its closest approach to Earth until January 27. Saturn passes less than a degree to the south of an open star duster called the Beehive, in Cancer, at the end of January.

The Moon is new on December 1 at 10:01 A.M. It waxes to first quarter on the 8th at 4:36 A.M. and to full on the 15th at 11:15 A.M. Our satellite wanes to last quarter on the 23rd at 2:36 P.M. It is new for a second time in December on the 30th at 10:12 P.M.

In January the Moon waxes to first quarter on the 6th at 1:56 P.M. and then to full on the 14th at 4:48 A.M. It wanes to last quarter on the 22nd at 10:14 A.M. and to new on the 29th at 9:15 A.M.

The Geminid meteor shower is one of the best annual showers. It is so named because the meteors appear to come from the constellation Gemini, the twins, which rises in the eastern sky during the evening, This year, however, a nearly full Moon during the predicted peak of the display--on the night of December 13-14--could make the shower hard to see. Try looking two nights before the peak, when there are short moonless intervals just before dawn.

A celestial holiday gift arrives on Christmas morning for those living in parts of the Pacific Northwest and the northern Rockies: the waning crescent Moon occults, or passes in front of, Spica. The star disappears along the Moon's bright limb, then pops back into view along the dark limb. In Seattle, Spica disappears at 5:21 A.M. Pacific standard time and reappears at 5:45 A.M. In Great Falls, Montana, the occultation begins at 6:16 A.M. mountain standard time and ends an hour later. Elsewhere, the Moon either barely misses Spica or the occultation takes place after sunrise.