By Deane Morrison

The bright winter stars are finally taking center stage, and Jupiter—long a morning planet—follows them into the evening sky.

The winter stars behave like a royal court. Not only do they boast many of the brightest stars, but the most luminous is the last to make its grand entrance. That’s Sirius, in Canis Major, a white beacon to the southeast of Orion’s majestic form. Orion is easy to spot, with its anchor stars Rigel, Betelgeuse, Bellatrix and Saiph; the three stars of the belt; and the hanging sword, an area of intense star formation.

Just nine light-years distant, Sirius outshines all other stars. The bright star above and east of it is Procyon, in Canis Minor, whose name means “before the dog,” a reference to how it rises before Sirius, the Dog Star. The two “Canis” constellations are Orion’s hunting dogs, and the dog days of July and August were so named because the ancients believed that due to the Dog Star’s proximity to the sun during those weeks, its heat combined with the sun’s to cause the hot, sticky weather.

The winter stars will be up by 11 p.m.—earlier as the month goes on—with Jupiter trailing them to the east. Jupiter outshines even Sirius, and its pale yellow color also distinguishes it from the lovely star. On the 9th, Jupiter begins retrograde, or westward, motion against the background of stars. This happens when Earth gets close to lapping the giant planet, which it will do in early February.

Mars continues to hold its ground in the evening sky, setting about three hours after the sun all month long. A crescent moon appears just west of Mars on the 24th; this pairing may help you find the Red Planet.

Saturn is gaining altitude in the southeastern morning sky, and Venus in the southwestern evening sky. Both will be easier to see next month.

The Geminid meteor shower peaks around midnight on the 13th, but you may see nice meteors a few nights on either side of the peak. The meteors radiate from Gemini, just northeast of Orion.

December’s full moon follows a high trajectory across the sky, reaching perfect fullness at 6:27 a.m. on the 6th. But it sets close to sunrise, so if you’re up, don’t delay in getting out to see it. This moon is known as the full cold moon, or the full long nights moon, a nod to the winter cold’s habit of settling in at this time of year.

As for our dwindling sun, it dips to its lowest point with the winter solstice, which occurs at 5:03 p.m. on the 21st. At that moment the sun reaches a point directly over the Tropic of Capricorn, and the sunny side of Earth will be lighted from the Arctic Circle all the way around to the Antarctic Circle on the other side of the planet.

Thanks to irregularities in Earth’s orbit, the earliest sunset occurs before the solstice. For example, in the Twin Cities the sun sets at 4:32 p.m. from the 4th through the 15th; in Duluth, it sets at 4:20 p.m. from the 6th through the 14th. But the latest sunrise doesn’t happen until early January. All in all, the day length changes very slowly in December, so it’s not hard to see where the solstice—which means “sun standing still”—got its name.

The University of Minnesota offers public viewings of the night sky at its Duluth and Twin Cities campuses. For more information and viewing schedules, see:

Duluth, Marshall W. Alworth Planetarium: www.d.umn.edu/planet

Twin Cities, Minnesota Institute for Astrophysics (during fall and spring semesters): www.astro.umn.edu/outreach/pubnight.

Check out the astronomy programs at the University of Minnesota’s Bell Museum ExploraDome: www.bellmuseum.umn.edu/ForGroups/ExploraDome/index.htm.

Contact: Deane Morrison, University Relations, (612) 624-2346,morri029@umn.edu