This week begins with a delicate crescent moon at dawn and builds toward a celestial crescendo -- a new moon, "shooting stars" and the official arrival of the winter solstice. The Geminid meteor shower may be wrapping up, but here comes the Ursids -- and don't forget Jupiter, masquerading as the "Christmas Star." If you have access to dark skies and a warm coat, this week promises awe-inspiring moments under a sparkling winter sky.
Here's everything you need to know about the night sky this week:
Monday, Dec. 15: Crescent Moon, Spica And Mercury
Look low in the southeast about an hour before sunrise to spot a waning crescent moon, just 18%-lit. Above is bright star Spica in the constellation Virgo while below is tiny Mercury.
Friday, Dec. 19: New Moon
At 8:45 p.m. EST, the moon reaches its new phase -- meaning it's absent from the sky entirely. This brings one of the darkest nights of the month, perfect for spotting the winter Milky Way. From a truly dark location, you'll see it arc softly across the sky from Cassiopeia in the northwest down to Orion and Canis Major in the southeast. It's less bright than summer's Milky Way, but rich in starfields.
Saturday, Dec. 20: A 'Christmas Star'
Shining brilliantly in the east after sunset, Jupiter takes center stage for the next month or so. At magnitude -2.6, it rivals Sirius -- the brightest star in Earth's night sky -- and makes a fine "Christmas Star" of its own. It rises with the stars of Gemini -- Castor and Pollux -- and remains visible through the night.
Planetary conjunctions (like those involving Jupiter) have been proposed as explanations for the biblical Star of Bethlehem.
Sunday, December 21: Winter Solstice As Ursid Meteor Shower Peaks
Winter officially begins in the Northern Hemisphere at 10:03 a.m. EST. Just after sunset, a 4%-lit waxing crescent moon will hover low in the southwest, setting shortly after. That leaves dark skies for the Ursid meteor shower, which peaks tonight.
It's a minor shower -- expect only around 10 meteors per hour -- but it's perfectly timed with the new moon this year, so is worth a look. Gaze roughly north, between the Big and Little Dippers, for meteors streaking across the sky from comet 8P/Tuttle's debris trail.
Star And Constellation of The Week: Sirius And Canis Major
Home to Sirius, Canis Major is now rising in the southeast by mid-evening. Representing the "Great Dog" that follows Orion the Hunter, this constellation contains a cluster of stars that seem to chase across the sky. Sirius itself lies just 8.6 light-years away and appears as a brilliant white-blue beacon. Try tracing the rest of the dog's outline below it.
The times and dates given apply to mid-northern latitudes. For the most accurate location-specific information, consult online planetariums like Stellarium.
Wishing you clear skies and wide eyes.