Full Cold Moon Stuffs The Night With Light

A striking halo circled the moon briefly last night over Duluth, Minn. when a veil of cirrostratus cloud passed overhead. Ice crystals in the clouds refracted or bend the light to form a circle. This type of halo is called a  22-degree halo because the distance across the sky from the moon to the halo’s edge is 22 degrees. Credit: Bob King

Never was there a better named full moon than the Cold Moon. That’s the one you’ll see tonight, hanging up there in Gemini like some rogue ornament. Bucketfuls of moonlight spilled across my snow-covered yard last night, truly a beautiful sight. Radiant nights. That’s what December brings around full moon time. Snow magnifies the effect, so that being outside feels like a living in the land of Tchaikovsky’s Nutcracker Ballet, where all’s a glitter.

Aldebaran is pictured moments before the moon occulted it last night. The star was surprisingly easy to see through binoculars so close to such a bright moon. It seemed to burn like a distant flame. Credit: Tom Ruen

Tonight, the moon will be full and even brighter than last night. I can’t wait. Crunchy snow and powerful moonlight join together to encourage us outside in spite of the cold.

You’ll notice tonight that the moon is super high up in the sky especially if you’re out late. That’s because it’s straddling the border of Gemini the Twins and Taurus the Bull, the highest point in the sun’s yearly path around the sky. Recall now those steamy days of early summer, when the sun rose w-a-y too early and set long after dinnertime. It occupied the very same spot the moon will tonight — Gemini-Taurus.

On this year’s Dec. 21 winter solstice,  the sun (yellow circle) reaches its lowest point on its yearly path around the sky. Immediately after, it begins to move north again, and the amount of daylight begins to increase until it reaches its highest point on the first day of summer. Because of Earth’s tilted axis, the sun swings high and low during a year’s time. Credit: Durham University Community

In the six months that have elapsed since then, Earth’s orbital motion combined along with its titled axis have rolled the sun down the hill, so to speak. Now, it shines from near its lowest point in the sky in the constellation Sagittarius the Archer, better known as the Teapot.

Just as you can’t see Gemini and its neighbor, Orion, in the summertime because they’re in the daytime sky alongside the sun, you can’t see Sagittarius in the winter sky. Since a full moon is always directly opposite the sun in the sky, the December moon always shines down from Gemini and Taurus, recalling warmer days.

It’s already moonrise in Italy. This fabulous photo of the full Cold Moon (also a supermoon!) was taken earlier today over Rome. Credit: Gianluca Masi

Don’t forget that tonight is the peak of the annual Geminid meteor shower. I casually spotted two bright ones last night while having a fun time watching the moon hide the star Aldebaran. Have you seen any yet? Step into the moonlight tonight and you just may!

While we’re on the topic of bright lights, I wrote a short guide for Universe Today called All I Want for Christmas Is a Green Laser for anyone interested in learning about and buying a green laser pointer. They’re super handy for pointing out stars and other nighttime sky objects.

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