By Andy Veh, for the Redoubt Reporter
Rising in the east and gaining altitude throughout the next two months are the great winter constellations.
Orion with its seven bright stars, among them red Betelgeuse and blue Rigel, as well as its stellar nursery, the Orion nebula, are quite prominent this month.
Other winter constellations visible in December are Taurus with red Aldebaran and its prominent star cluster, the Pleiades; Auriga, in the shape of a pentagon, with yellow Capella; Gemini with the twin stars Castor and Pollux; the head of Canis Major low on the horizon with the brightest star (aside from the sun) that we can see from Earth, Sirius; Procyon in tiny Canis Minor; and Regulus in Leo very late in the evening.
Because this region of the sky hosts seven of the 20 brightest stars as seen from Earth and because it contains quite a few easily recognizable constellations, it is my favorite region of the sky.
High in the south appears the Great Square of Pegasus in the shape of a diamond. Above it, close to the zenith, is Cassiopeia. Getting close to the western horizon — but never completely setting in Alaska — are the three stars that make up the summer triangle, Deneb in Cygnus, Vega in Lyra and Altair in Aquila (that one actually does set, just barely for a few hours).
In the north are Ursa Major’s Big Dipper and Ursa Minor’s Little Dipper, the latter always really close to 60 degrees, our latitude on the Kenai.
Planets in the evening and all night:
Mars, Neptune and Uranus are low on the southern horizon after sunset.
From the summer triangle follow Altair toward the horizon and you see a red object. That’s Mars. The crescent moon is right next to it on Christmas Eve. While Mars can be easily seen with the naked eye, binoculars are needed for the giant planets.
The same crescent moon joins Neptune on Christmas Day and Uranus on Dec. 28, now as a first-quarter half moon.
Jupiter rises just north of east around 10 p.m. early and around 8 p.m. later this month. It is quite close to Regulus. The gibbous moon joins the biggest planet in our solar system Dec. 10 and 11.
Venus is getting set for a great showing in early 2015. Right now, though, it barely appears on the southwest horizon, setting shortly after the sun.
In the morning, Saturn can be seen very low in the south around 8 a.m., making a large triangle with Arcturus above it and Spica to its right. The waning crescent moon is next to it Dec. 19.
The days are still getting shorter, though the pace has slowed. On Dec. 1, there are 6 hours, 19 minutes, of daylight.
On Dec. 21 (the solstice), there’s 5:43, but then it’s 5:53 on Dec. 31, since after the winter solstice, days get longer again.
Due to its not-completely perfectly circular, but ever-so-slightly elliptical orbit, Earth will be closest to the sun Jan. 4. Due to Kepler’s second law (the conservation of angular momentum), it is also its speediest at 67,800 mph, compared to its slowest of 67,200 mph when Earth is farthest from the sun in July. Its change of speed influences the length of the day, as well, and dictates that the latest sunrise occurs at 10:12 a.m. on Dec. 27 and its earliest sunset at 3:53 p.m. Dec. 16, neither of which is on the solstice, due to Earth being fastest in its orbit.
Andy Veh is an associate professor of physics, math and astronomy at Kenai Peninsula College.
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