The December Sky

Paul Curtin

Special Notes: The Geminid meteor shower should be worth observing this year. They peak the evenings of December 13-14. Unlike many other showers, one need not wait until the morning hours for these slow moving meteors. Look for the bright asteroid Iris in the dark region west of the Pleiades this month. The December issue of Sky and Telescope has a handy finder chart.

Looking north, the area between Cassiopeia and Camelopardalis contains some great fields for binocular sweeping. Look for the inverted Y shape of Perseus. Half way between alpha Persei and Cassiopeia is the Double Cluster, denoted h and chi Persei. This is a great sight with wide-field equipment. At the western “foot” of Perseus is Algol, an eclipsing binary that can go from maximum to minimum within five hours. Gupta has times for monthly minima of Algol. M34 is an open cluster that can be found by sweeping west of Algol. From very dark-sky sites one can try to glimpse the California Nebula near ksi Persei.

South of Perseus, hovering in otherwise unremarkable skies, is M45, the Pleiades. This bright blue cluster is easily one of the most popular open clusters, and it is often mistaken for the Big Dipper. It is a treat in telescopes of all sizes. From the Pleiades we move to the V- shaped cluster due east: the Hyades, with red Aldebaran on its eastern side. A sweep through this area shows that the Hyades, a much older cluster, contains a more varied star population than the Pleiades.

Eridanus wanders from the foot of Orion to the deep south. Along the western edge of Eridanus, especially in Fornax, we find a sprinkiling of faint galaxies. The most impressive region is the Fornax cluster of galaxies between sigma Eridani and chi Fornacis.

Eridanis ends at Achernar, the one truly bright star in this region. South of this we are met with little more than dim, uninteresting fields until the Large Magellanic Cloud arrives in January.

The Planets in December

Mercury is in the morning sky.

Venus is a difficult twilight object.

Mars is in the morning twilight.

Jupiter is an early morning object.

Saturn is in Leo and can be observed after midnight.


Bibliography

Burnham, Robert Jr., Burnham's Celestial Handbook, New York: Dover, 1978.

Gupta, R. (ed.), Observers Handbook 2006, Toronto: University of Toronto Press, 2005.

Kepple, G. R., Sanner, G. W., The Night Sky Observers Guide, Richmond, Virginia: Willman-Bell, 1999.

Tirion, W., Rappaport, B., Remaklus, W., Uranometria Deep Sky Atlas, Richmond, Virginia: Willman-Bell, 2000.

Webb, T. W., Celestial Objects for Common Telescopes, New York: Dover, 1962.