The December Sky

Paul Curtin

Mars is at opposition this month. We have a mere two months to try to view some surface features on the red planet.

December in the north brings the Milky Way back to the night sky. This, after the somewhat bleak Autumn sky, is a welcome sight. That said, one must acknowledge that the polar region seems reluctant to follow this new trend. We begin this month with a large collection of stars east of Cassiopeia known as Camelopardalis. Navigating this constellation can be a challenge as there are no outstanding forms useful for reference. Find alpha and beta and then become familiar with the fields of neighboring Cassiopeia and Perseus. Use these stars to hop to the open cluster NGC 1502 and the planetary nebula NGC 1501. These may require telescopes to appreciate but nearby is the asterism known as Kemble’s Cascade, best viewed in binoculars. There are also a number of multiple stars in this region including beta, a fine triple.

South of Cassiopeia is the distinct figure of Perseus: two lines running south from the double star eta. Near the foot of the western line is beta, the binary variable Algol. North and west of Algol is the open cluster M34. Compare this cluster with the double cluster north and west of eta. These clusters, NGC 869 and 884, are best observed in binoculars or wide-field telescopes. In dark skies, start at eta, then scan west to find phi Andromedae, then carefully edge northward until you find M76, the little dumbbell. In very dark skies look for the emission nebula NGC 1499, the California Nebula. The Milky Way runs through Perseus, so scan slowly to find the numerous open clusters scattered throughout this constellation.

South of Perseus we find one of the most famous open clusters, M45, the Pleiades. This charming object, sometimes mistaken for the little dipper, occupies the shoulder of Taurus. M45 is best viewed in binoculars. In telescopes its distinctive shape is lost although with large telescopes in clear skies one may glimpse the blue reflection nebula surrounding some of the stars. to the east we see the other major cluster in Taurus, the v-shaped Hyades, with bright Aldebaran on the eastern tip. Aldebaran is not an actual member of the Hyades but stands between the cluster and earth. Try to find M1, the Crab nebula, near zeta. It can be hard to locate but this fuzzy supernova remnant is unique among the Messier objects.

Leaving Orion until next month, we follow Eridanus as it winds it way south all the way to bright Achernar. This long string contains many multiple stars. See if you can glimpse the reflection nebula IC2118, the Witch-head Nebula, shining by the light of Rigel. The source star’s brilliance may hamper your efforts, so it is important to keep Rigel out of the field of view.

In the south the earl summer sky contrasts greatly with the northern sky. Wrapped into the length of Eridanus is the galaxy-sprinkled form of Fornax. Large telescopes are needed to truly appreciate many of these objects, but it is worthwhile to simply catalogue how many you can find.

The Planets in December

Mercury can not be easily observed this month.

Venus is a very bright morning object throughout December.

Mars moves into Taurus and reaches opposition there on the 24th. Look for it near the moon on December 23 and 24.

Jupiter begins to slip behind the sun this month.

Saturn is visible in the late night sky.

Bibliography

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

Kelly, P. (ed.), Observers Handbook 2007. Toronto: University of Toronto Press, 2006.

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.