Constellations make holiday skies sparkle

The Sky Guy

Posted: Sunday, December 03, 2006

 

  Graphic courtesy of Andy Veh

Graphic courtesy of Andy Veh

Last month’s Mercury transit was a great success, owing mostly to clear skies and it happening in the middle of an Alaska winter day. About 100 people showed up to look through my telescopes and at projected images of our sun, showing a beautiful sunspot and of course the transiting Mercury moving across our sun’s surface. Thanks also go to my students who helped set up, specifically Mike Stacy, and to Scott Moon who shot and published a nice transit photo. Enough self-accolades.

The accompanying chart shows the evening sky during December, 8 p.m. early and 6 p.m. late in the month. Stars with an asterisk are marked as dots in the chart.

Still high in the sky is the “summer” triangle, made up of Lyra’s Vega*, Cygnus’ Deneb* — a long-necked swan shown as the northern cross on the chart — and Aquila’s Altair*. From south to north are several prominent constellations: the great square of Pegasus, also appearing as a baseball diamond with Markab at home base and Scheat, Alpheratz and Algenib on first, second and third base, respectively; the “W” of Cassiopeia with its brighter stars Schedar and Caph; the fainter house of Cepheus; the Little and Big Dippers of Ursa Minor and Major — the small and large bears; and the bear-watcher Bootes which is setting in the north.

Ursa Minor’s brighter stars are Polaris, which is within 1 degree of the north celestial pole, and Kochab. Ursa Major’s prominent stars are Merak and Dubhe in its dipper, which also are the pointer stars for Polaris. Polaris derives its fame from being the pole star and therefore very important for navigation. A common mistake is to assume it appears very bright while in fact there are 48 brighter stars seen in the sky. Also in Ursa Major is the double star Mizar and Alcor in the bend of the handle.

Orion, the Hunter, is about to rise. It is many people’s favorite because of its brilliance. Four stars arranged in a rectangle — red Betelgeuse*, blue Rigel*, Bellatrix, and Saiph — outline the body, while three stars make up the belt — Alnitak, Alinalam, Mintaka — with the Orion nebula as the sword beneath it.

Above Orion you find Taurus, part of it in the shape of an arrowhead including red Aldebaran*. Above that are the Pleiades*, or Seven Sisters, a must for binoculars. To Taurus’ left is the pentagon Auriga with yellow Capella*. Beneath Capella appear Castor* and Pollux*, the twins in Gemini. We close this circle toward the horizon with Procyon and Sirius, the brightest star in the sky, both of which rise about two to three hours after Orion.

Along with these starts the only visible night planet this winter will rise. Around midnight notice two bright objects above the eastern horizon. The lower one is Regulus, the brightest star in Leo, the Lion, a constellation easily recognized as such. The other object is our solar system’s gem, Saturn. In high-powered and stabilized binoculars or in low-power telescopes one can get a hint at its rings and see its brightest moon, Titan.

For early risers, watch Orion setting in the west just before dawn. Regulus and Saturn will appear high in the south. Around Dec. 14, the Geminid meteor shower will be at maximum with up to 75 meteors per hour. However, light from the waning moon will interfere. Still, at that rate it may be the year’s best meteor shower, even outdoing the Perseids in August which battle the all-too-bright Alaska summer nights. While almost all meteor showers are associated with debris from comets, the Geminids derive from the asteroid Phaeton’s jetsam.

Later in the month Jupiter can be glanced very low in the southeast just before dawn. Mars and Mercury would join the giant planet, too, but they’re rising too late in Alaska skies.

Andy Veh is a professor at Kenai Peninsula College. He can be reached at aveh@uaa.alaska.edu.



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