The Full Cold Moon

Hey, Sky Fans! December’s full Moon, my favorite, is called the Cold Moon, and will be in your skies starting around sunset this coming Wednesday, the 13th. What? You say you don’t have a favorite full Moon, too?

The Cold Moon name is used because it’s usually the closest full Moon to the winter solstice, when the nights are at their longest and coldest. But, since December’s solstice is on the 21st, the closest full Moon to the solstice could turn up in January.

Anyhow, full Moons rise and set with the Sun, and, here in the northern hemisphere, December’s days are the shortest, so this month’s full Moon will be riding high up into the sky for a long time overnight; much longer than July’s full Moon is in the sky. In fact, the Moon rises so early this time of year that, a couple of years ago, I remember seeing a gorgeous orange-looking Moon rising over the highway as I was driving home from work. As the road turned toward the east, there it was, giant and brilliant. I’ve often wondered how many of the other people with me on the road thought it was as amazing a sight as I did.

A 1999 Full Moon (from NASA)

As if all of this wasn’t enough, this month’s full Moon is the third perigee full Moon in a row; you may have seen these called “Supermoons.” As we’ve talked about, the Moon’s orbit around the Earth isn’t perfectly round; it’s a somewhat-elongated ellipse. On average, the Moon is 238,000 miles, 383,000 km from the Earth. Since it’s an ellipse, there’s are points that are the farthest (apogee, around 250,000 miles / 406,000 km) and closest (perigee, about 221,000 miles / 356,000 km).

When the Sun-Earth-Moon line is straight, which put the Moon into its full Moon phase, when the Moon is near perigee, it looks a bit bigger and brighter in the sky, and some of us call it a supermoon. I don’t really like the word, myself, but that’s just my preference. Whatever you like to call it, I hope you have a chance to see it. By contrast, sometimes people call an apogee full moon a micromoon, but not a lot of people want to yell and scream about how incredible the smallest and least bright Moon is, I guess.

December’s full Moon is a really special one because it rises so early and makes its way so high overhead through so much of the night. Add in the this festive time of year and it’s really wonderful. I hope you have a chance to see it, and see why it’s my favorite.

Clear skies, everyone!


2 thoughts on “The Full Cold Moon

  1. Yeah, I like that one. There’s another good one out there, too, but I’m too undercaffeinated at the moment to look for it. I like what Dr. Tyson said around the time of Novemnber’s full Moon. It was something like “This month’s supermoon is really only super if you think a pizza that’s 16 inches across is less super than one that’s 16.03 inches across.” I love Dr. Tyson’s work, though I sometimes get tired of the nihilistic view he takes (or the person who does his social networking takes), but that made me laugh.


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