A little about the 2 occurrences tonight, with the December Full Cold Moon, and it also being a Supermoon…
When the “Full Cold Moon” rises on Sunday night (Dec. 3) it will also mark the first (and last) “Supermoon” of 2017.
Supermoons happen when a full moon approximately coincides with the moon’s perigee, or a point in its orbit at which it is closest to Earth. This makes the moon appear up to 14 percent larger and 30 percent brighter than usual. The moon becomes totally full at 10:47 a.m. EST (1547 GMT) on Sunday (Dec. 3). It will officially reach perigee less than 24 hours later on Monday (Dec. 4) at 3:45 a.m. EST (0845 GMT), when it is 222,135 miles (357,492 kilometers) away from Earth.
December’s supermoon is actually the first of three back-to-back supermoon full moons to come in the next two months. On Jan. 1 and Jan. 31, the full moon will also occur near the moon’s arrival at perigee, according to NASA, which billed the line up as a supermoon trilogy. The Jan. 31 supermoon is also the second full moon of January, making it a Blue Moon, and also occurs during a total lunar eclipse.
What is a Supermoon?
While the moon’s average distance is 238,000 miles (382,900 km) from Earth, its orbit isn’t perfectly circular, so that distance varies a small amount. When it reaches apogee, or its farthest distance from Earth, on Dec. 19, it will be 252,651 miles (406,603 km) away. That’s a difference of 30,516 miles (48,110 km) — but the moon’s distance from Earth can vary more than that.
The perigee for December’s supermoon won’t even be the closest this year; that happened May 25, when the not-so-super new moon was 221,958 miles (357,208 km) away from Earth. That date didn’t coincide with a full moon, though, so it didn’t qualify as a supermoon.
Supermoons don’t happen every month because the moon’s orbit changes orientation as the Earth goes around the sun. So, the long axis of the moon’s elliptical path around the Earth points in different directions, meaning that a full (or new) moon won’t always happen at apogee or perigee.
How the Full Cold Moon got its names
According to the Old Farmer’s Almanac, the name of the full moon in December is “Full Cold Moon,” and given the weather in December (at least in the Northern Hemisphere), that’s not a surprise.
This is also reflected in the names from native peoples of North America. According to the Ontario Native Literacy Project, the Ojibwe called December’s full moon “Mnidoons Giizis,” the “Big Spirit Moon” or “Blue Moon.” For the Ojibwe, it marked the 12th calendar month, and was a time for healing. The Haida of the Pacific Northwest called it the “Snow Moon,” or “Ta’aaw Kungaay.”
Among the Hopi, whose ceremonial life revolved around the lunar and solar cycles, the lunation just before the winter solstice was the “Sparrow-Hawk” moon, as noted by Janet Sharp of Washburn University in her study of Hopi mathematical concepts and teaching.
In the Southern Hemisphere, December is summertime. The Māori of New Zealand described the lunar months in November to December as Hakihea, or “birds are now sitting in their nests,” according to the Encyclopedia of New Zealand.
In China, the traditional lunar calendar calls the December lunation the 10th month. Called Yángyuè, or Yang month, it’s named for the yang ― the masculine, positive principle of Taoism familiar to Westerners as part of the yin and yang.