December nights are usually cold on the Western Slope, but there are some great celestial treats for those willing to endure the frigid temperatures.
At around 6 p.m. on December 2, look to the southwest. If skies are clear, you’ll see brilliant Venus just to the left of a crescent moon, with reddish Mars above and to the left of Venus. If you have binoculars, take a closer look at the Moon. Along-side the bright, sun-illuminated crescent, you may also see faintly part of the dark, night-side of the Moon. This is called Earthshine. As seen from the near-side of the Moon tonight, the Earth is nearly full and is casting blue-gray Earthshine across the lunar landscape. The Moon reaches first quarter on December 7 and is full on December 14. But, the bright light of the full Moon will hinder viewing of the Geminid Meteor Shower, which peaks on the night of December 13 to 14.
Between December 8 and 18, you may see the planet Mercury shortly after sunset, if you have an unobstructed view to the southwest and clear skies.
December 21 marks the winter solstice in the northern hemisphere, which brings us our longest night and shortest period of sunlight. Also on December 21, the Moon reaches last quarter, so evening skies are dark. Late December is a great time to start enjoying the bright stars and constellations of winter, including constellation Orion, which rises in the east by 6:30 PM. And, Sirius, the brightest star other than the sun, dazzles us by 8:30 PM in the southeast. On late December’s dark evenings, we can also enjoy the glow of the Milky Way, spanning the constellations Cygnus in the northwest, to Cassiopeia, nearly overhead, through Auriga and Gemini in the northeast and east. So brave the cold for at least a few minutes, and enjoy the spectacles of our December night sky!
Western Slope Skies is produced by members of the Black Canyon Astronomical Society. This episode was written and recorded by Art Trevena.