Round We Go
The cold crisp air that might otherwise keep you inside provides some of the clearest and darkest skies of the year, so even with this week’s bright moon, some major stars and constellations stand out against its glare.
Sunset Thursday finds the near-full moon high in the east, between Betelgeuse, the shoulder of Orion, below, and the twins of Gemini, Pollux and Castor, above. From these two stars wends the stars the Great Winter Circle, more aptly called the Great Winter Hexagon, which contains seven of the 23 brightest stars.
To trace this asterism, begin with blueish-white Pollux (17), then look to honey-orange Castor (23) higher in the north. From there shoot to the northeast to golden Capella (6) of the constellation Auriga the charioteer. Next, drop southwest to red Aldebaran (14), the eye of Taurus the bull. Now shift your gaze to Orion’s foot, blue-white Rigel (7). Farther south is the hunter’s great dog, Canis Major, marked by Sirius, the brightest star in the heavens. Back to the northeast you’ll find the Little Dog Canis Minor and its lead star Procyon (8). Return to Pollux and you’ve closed the loop. While not part of the circle, Betelgeuse sits right in the middle and is the 10th brightest star.
As the sun sets Saturday, January’s full Wolf Moon climbs into the eastern sky, trailing Castor and Pollux and to the left of Procyon. By Monday the now-waning gibbous moon has left behind the Great Circle and is just a few degrees to the south of another stellar luminary, Regulus (21), the heart of Leo the lion. Tuesday the moon is midway between Regulus to the west and Jupiter to the east. Wednesday night through dawn next Thursday, the moon is 10 degrees below Jupiter.
Brighter than any star, Jupiter rises due east just after 9pm and is at its highest in the south at 3am. By that time Mars, rising around 1:30am, will be well above the southeast horizon. Saturn rises just after 4am, followed 90 minutes later by Venus, brighter than all but the sun and moon. Saturn and Venus are about 15 degrees apart, but the Morning Star sinks lower day by day while Saturn inches higher. As the coming sun starts to glow in the east, see if you can spot Mercury low against the horizon; binoculars may help spot this last of the naked-eye planets.