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Sky Watch
by J. Alex Knoll
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Winter’s Dark, Early Nights
While the year’s earliest sunset is already past, these cold nights are still getting longer.
Thursday’s waning gibbous moon rises in the northeast a few hours after sunset. December 7th marks the earliest sunset of the year, nine seconds shy of 4:46. While winter solstice December 21 is the shortest day of the year, Earth’s elliptical orbit around the sun skews the earliest sunset and the latest sunrise, which isn’t until January 5.
Each evening the moon rises more than an hour later. Over the course of the week it passes four of the familiar constellations of the zodiac, Gemini, Cancer, Leo and Virgo in pre-dawn skies Wednesday.
While these pairings may make it easier to locate a constellation, it’s hard to compete when the moon passes close to a planet, as it does this week. Around 9:30pm Saturday the moon crests the northeast horizon with Saturn three degrees behind. Regulus, the heart of Leo the lion, trails farther behind but is only a bit dimmer than the ringed planet. As the moon and Saturn climb higher into the east, hour after hour they grow closer together. By 3am Sunday, less than one-and-one-half degrees separate the two. But it isn’t until an hour before sunrise (7:15am) that they are less than one-half degree apart high in the south.
By Wednesday and Thursday, the waning crescent moon rises well after midnight and, more important, is far from the constellation Gemini. That’s the radiant source of the shooting stars from the annual Geminid meteor shower, which offers two peaks, the evening/morning of the 13th/14th and again on the 14th/15th.
The Geminids should more aptly be called a comet shower, as it alone is spawned by debris in the wake of a comet, named 3200 Phaethon, rather than a meteor.
