The full moon of December, called the Full Cold Moon, will arrive overnight tonight just after midnight EST on Thursday, Dec. 12, and as it rises it will be joined in the sky by the planets Venus and Saturn, which will be close together after reaching a conjunction on Dec. 11.
The moon becomes officially full on Dec. 12 at 12:13 a.m. EST (0513 GMT).
Passing through the constellation Taurus, our planet's satellite will rise around 4:18 pm. on Dec. 11 for observers on the U.S. East Coast. The sun sets about 10 minutes later, and observers looking west will see Saturn and Venus in the sky together only a few degrees apart, and Jupiter will be visible as well, though it is difficult to see as it will be just a degree above the horizon by 5 p.m. local time.
The moon itself will be framed by Auriga, the charioteer, to its left (north) and the Hyades star cluster to the south (on the right). The Hyades usually defines the "head" of Taurus, though its fainter stars will be washed out by the lunar glare.
Planets to see
The two planets Venus and Saturn will be in conjunction — sharing the same celestial longitude — on Dec. 10, and at 11:41 p.m. EST (0441 GMT on Dec. 11) will get as close as 1.8 degrees, or a bit more than three lunar diameters, according to In-the-sky.org. The actual conjunction won't be visible from New York City; the planets will set by 4:49 p.m. local time In New York, but they will still be a distinct pair. Both will be in Sagittarius.
Catching the actual conjunction will require moving west; Observers in Hawaii will see the conjunction at 6:41 p.m. local time, and the pair doesn't set until 8:02 p.m., well after the sun (which sets at 5:50 p.m.).
Jupiter will be approaching its superior conjunction, which occurs on Dec. 28. Superior conjunction is the point where the planet is on the opposite side of the sun from Earth. That means it is sinking into the solar glare at sunset through December. On the night of the full moon the planet sets at 5:15 p.m. local time in New York City, while the sun sets at 4:29 p.m., so Jupiter will be hard to see, and most observers will only catch it for a few minutes even with clear weather and an unobstructed horizon.
Mars, by contrast, will be visible to observers who are up early (or have stayed up late). On Dec. 12 the Red Planet will rise at 4:20 a.m. in New York, while the sun doesn't rise until 7:10 a.m. local time. So, early commuters can look east and see Mars a good 20 degrees above the southeastern horizon by 6:30 a.m., as the sky gets lighter.
Full moons are so bright that they tend to overwhelm fainter objects in the night sky, even from dark-sky locations. Indeed, the full moon casts distinct shadows. Even so, the winter sky offers some of the brightest constellations of the year.
Besides Auriga and Taurus, by about 9 p.m. in your local time on the night of Dec. 11, one can see Orion, the hunter and its distinctive belt of three stars to the right and downward, toward the south of the moon, and to the left Gemini's brightest stars, Castor and Pollux, will also be evident. The brightest star in the Northern Hemisphere sky, Sirius, will also be rising and visible almost the entire night.
In the Southern Hemisphere, the Large Magellanic Cloud, a dwarf galaxy that is the Milky Way's companion, is visible all night from locations such as Melbourne, Australia, because from that latitude it is circumpolar — it never sets. On the night of the full moon (Dec. 12) the Large Magellanic Cloud reaches its highest point at about midnight. Even with the near-full moon it is relatively easy to observe.
The constellations of Puppis, Vela and Carina, which collectively make up the Ship (also known as Argo Navis) will be high in the southeastern sky by 9 p.m. local time, and Canopus, the brightest star in the Southern Hemisphere, can be easily spotted.
A moon of many names
The December full moon is often called the Full Cold Moon, according to the Old Farmer's Almanac, as that's what the weather tends to be like in North America or Europe. While names for the full moon in the United States and Canada are adapted from Native American terms, nations in the Americas had diverse names and traditions.
According to the Ontario Native Literacy Project, the Ojibwe (or Anishnabeg) peoples called it Mnidoons Giizis, the Big Spirit Moon or Blue Moon. (This is not the same as the "blue moon" that is a second full moon in a single calendar month). The Cree called it the Thithikopiwipisim, or Hoar Frost Moon.
In the Pacific Northwest, the Haida called December's full moon the Snow Moon, or Ta'aaw Kungaay, while the Tlingit called it Shanáx Dís, meaning "unborn seals are getting hair," according to the Tlingit Moon and Tide Teaching Resource published by the University of Alaska at Fairbanks.
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 that appeared in the February 2015 edition of the Journal of Mathematical Culture.
In the Southern Hemisphere, December is during the summer, and the Māori of New Zealand described the lunar months in November to December as Hakihea, meaning "birds are now sitting in their nests," according to the Encyclopedia of New Zealand.
In China's traditional lunar calendar, the December lunation is the 11th month of the year. Called Dōngyuè, meaning "winter month," it marks the winter solstice.
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