December’s full moon, called the Cold Moon, falls on Dec. 7th for people in the Eastern Time Zone and points west. Our satellite will be accompanied by three easily visible planets as it rises, and be situated among the Northern Hemisphere’s brightest winter constellations, in Taurus. Observers in parts of North America and Europe can also see the moon pass in front of Mars, a phenomenon called an occultation.
The moon becomes officially full at 11:08 p.m. Eastern Time in New York City (0408 GMT on Dec. 8), according to the U.S. Naval Observatory (opens in new tab). For New York City observers, the moon will rise that evening at about 4:58 p.m., and set at 6:41 a.m. the morning of Dec. 8. The timing of lunar phases depends on the moon’s position relative to the Earth and the sun; a full moon is when the moon is 180 degrees away from the sun (using the Earth as the center of the circle). The hour of the full phase depends only on one’s time zone – the full moon is at 10:08 p.m. in Chicago or Mexico City, and 8:08 p.m. on the West Coast. Meanwhile the full moon happens at 12:08 a.m. on Dec. 8 if one is located in much of Brazil or Venezuela, while in Paris, it occurs at 5:08 a.m. For observers in New Zealand (just on the other side of the International Date Line from the U.S.) the moon becomes full at 4:08 p.m. on Dec. 8.
If you’re looking to snap a photo of the December full moon, check out our guide on how to photograph the moon. If you don’t have everything you need to photograph the night sky, consider our best cameras for astrophotography and best lenses for astrophotography.
Related: Full moon calendar 2021: When to see the next full moon
On Dec. 7, the moon will be in the sky at the same time as three naked-eye planets: Saturn, Jupiter and Mars (Mercury and Venus will technically be up, but both are so close to the sun on that date that they are very difficult, to see). If you are in the United States, Mexico and Canada north of a line running roughly from the southern tip of Baja California to Maine, Europe west of Russia and north of the Alps, or Greenland, one can watch the moon pass in front of Mars.
The occultation isn’t visible across the whole Earth because the moon is relatively close, much closer than other planets. That means its position against the background stars will differ depending on latitude and longitude.
Read more: The brightest planets in December’s night sky: How to see them (and when)
The International Occultation Timing Association has a list of times for different locations (opens in new tab). In the U.S., for example, observers in Detroit will see Mars disappear behind the moon at 10:20 p.m. Eastern and reappear at 11:08 p/m. Near the southwestern boundary of the region of visibility, the city of Hermosillo, Mexico, will see the occultation start at 7:30 p.m. local time and end at 8:19 p.m. Near the northern limit is Juneau, Alaska, where the occultation will start at 6:19 p.m. local time and end at about 6:55 p.m. In Europe, Icelanders in Reykjavik will see Mars slip behind the moon at 4:31 a.m. on Dec. 8, and emerge at 5:35 a.m. In Paris, the occultation starts at 5:04 a.m. local time and ends at 6:02 a.m. (The moon doesn’t set there until 9:03 a.m. on Dec. 8 and the sun doesn’t rise until 8:30 a.m.).
For regions where the occultation isn’t visible (as in New York City), the full moon will still be well above the horizon by about 5:30 p.m. EST (2230 GMT) on Dec. 7, and will appear above and to the right of Mars. As one looks further to the right (westward) one will see Jupiter, about 45 degrees high, recognizable as it is one of the brighter objects in the sky and shines with a steady, yellow-white light. (The width of your fist at arm’s length equals roughly ten degrees in the sky.)
Moving one’s attention further west, one will see Saturn, which is fainter than Jupiter but also shines steadily – one of the ways to know you are looking at a planet rather than a star is that stars will twinkle under some conditions, whereas planets will not. The days in December are short – the sun sets in New York at 4:28 p.m. EST (2128 GMT) on Dec. 7, so the sky will be dark enough to make spotting planets relatively easy.
The moon will be in Taurus, the Bull, and by about 7:30 p.m. EST (0030 GMT on Dec. 8) just to the right (west) and south (below) will be Orion, whose three “belt” stars (Alnilam, Alnitak, and Mintaka) are bright enough that the moon won’t wash them out. Meanwhile north of Taurus – to the left in the first half of the night – is a yellowish star called Capella, the brightest in Auriga the Charioteer. An hour later Gemini is above the horizon and low in the northeast. By 10:00 p.m. EST (0300 GMT on Dec. 8), Procyon and Sirius, two bluish-white stars that are the brightest in Canis Minor (the Little Dog) and Canis Major (the Big Dog) have come up. Sirius is the brightest star in the sky, and marks the head and neck of the Dog.
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In the Southern Hemisphere, it’s summer, so the sun sets later – at 7:48 p.m. local time in Cape Town, South Africa, on Dec. 8. The just-past-full moon rises that evening at 8:25 p.m. By 9 p.m. Canopus, the brightest star in Carina, the Ship’s Keel, is 36 degrees high in the southeast. To Canopus’ left (east) one sees Canis Major and Orion “upside down” and the moon and Mars, which will appear further away from each other than in New York City. The planet will also be higher in the sky than the moon, since one is also seeing the moon and Mars “upside down.” Meanwhile hear the feet of Orion, the constellation Eridanus the River begins, and one can follow its stars to Achernar, the end of Eridanus. Achernar is just east of south, and a full 66 degrees high.
The Old Farmer’s Almanac calls the December full phase the Cold Moon, and that is certainly true if you live in the Northern Hemisphere’s middle latitudes. But there are other ideas as to the significance of a December full moon. In China, the December lunation is called Dōngyuè, “Winter Moon.” The Hopi people named the month in which the winter solstice occurs the “Respected Moon.”
For the Māori, whose culture is indigenous to the Southern Hemisphere, the November-December lunation is lunation Hakihea, or “Birds are now sitting in their nests.” In China, the December lunation is called Dōngyuè, “Winter Moon.”
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