The full moon of January, called the Wolf Moon, will occur in the U.S. at 6:08 p.m. Eastern Time on Jan. 6, according to the U.S. Naval Observatory(opens in new tab). Moonrise in New York City is at 4:17 p.m.(opens in new tab) The moon will be in the constellation Gemini, and rises about 26 minutes before sunset, which is at 4:43 p.m. Eastern Time.
Full moons happen when the moon is exactly on the opposite side of the Earth from the sun. The moon looks illuminated because we see the sun’s light reflected from it, and because the moon’s rotation period is the same as its orbital period, we always see the same face of our satellite world.
Timing of lunar phases is the same everywhere, since it is determined by where the moon is relative to the Earth rather than its apparent position in the sky, which differs slightly depending on one’s location. Time zone generally determines the hour; observers in the British Isles and Portugal will see the moon become full at 11:08 p.m., while those in western continental Europe will see it at 12:08 a.m. Jan. 7. Pacific Time observers will see the moon become full at 3:08 p.m. – so the moment occurs well before moonrise – while those in eastern Asia and Western Australia (Seoul and Perth, for example) will see the moon officially full at 7:08 a.m. local time.
Since the full moon is on the opposite side of the sky as the sun, Northern Hemisphere observers will see it relatively high in the sky – essentially the moon is in the position the sun would be in the summer months. From New York City (and similar latitudes) this means the moon hits a maximum altitude of about 76 degrees; observers just a bit further south in Miami, Florida, will see it reach 89 degrees – nearly at the zenith at 12:42 a.m. on Saturday, Jan. 7. In the Southern Hemisphere the reverse is true, as it is summer there. In Melbourne, Australia, the full moon will reach a maximum altitude of only 24 degrees at 1:10 a.m. local time on Jan. 7.
The moon moves quickly against the background stars, because it is so close to Earth (relatively speaking), only 239,000 miles (384,000 km) on average – compared to tens of millions of miles for the nearest exoplanet. Approximately every hour the moon appears to move eastward by one of its own diameters, or about half a degree. One effect of this is that the moon takes longer than 24 hours to make a full circuit around the sky and reach its previous position. This means that on one day in each lunation (lunar month), the moon never crosses the local meridian, the line drawn through the zenith from north to south. Which day it is depends on one’s longitude, though it is always within a day or two of the full moon. In New York, it happens to be on the night of the full moon (Jan. 6), whereas in Melbourne (where the full moon happens at 10:08 a.m. Jan. 7) it is on Jan. 5.
On the night of the full moon, Mercury will be lost in the sun’s glare, and won’t come out again as a morning star for a few days (it starts to become visible for mid-latitude Northern Hemisphere sky watchers on about Jan 12).
Venus, however, will be just above the western horizon; at sunset it will be about 12 degrees high in the southwest in mid-northern latitudes. From New York City, it will become more easily visible about a half hour after sunset, when it is at an altitude of about nine degrees, though it will still be a challenge as the sky is still a bit light in the west. Observers further south will have an easier time of it; from San Juan, Puerto Rico, the sun sets at 6:02 p.m. on Jan. 6 and Venus is about 17 degrees above the horizon; by 6:30 p.m. it is still about 11 degrees high; offering a better chance to see it. The planet’s highest altitudes are near the equator; from Quito, Venus is 18 degrees high at sunset (which is at 6:23 p.m. local time on Jan. 6) and is still 11 degrees above the horizon a half hour later. As one gets below the equator Venus appears lower in the sky; at the latitude of Buenos Aires viewing is little different from New York.
After sunset on Jan. 6, as the sky gets dark, Saturn, Jupiter and Mars will all be visible from mid-northern latitudes across the southern sky. Saturn will be in the west, about 16 degrees above the horizon in the southwest. Looking left (eastward) one will see Jupiter, distinct because of its brightness, about 46 degrees high in the south-southwest direction. Further east, one will spot Mars, also about 46 degrees high and just south of east in the constellation Taurus.
Southern Hemisphere observers will see a similar sight, though later at night as it is summer there and the sun sets later. For example, if you live in Cape Town, where the sun sets at 8:01 p.m. on Jan. 7, about an hour later (9 p.m. local time) you’ll see Saturn in the west about 13 degrees high, with Jupiter to the northwest, about 34 degrees above the horizon. Mars will be almost due north, about 30 degrees in altitude as the moon rises in the northeast.
Northern Hemisphere skies are full of bright stars – Orion, Taurus, Gemini and Canis Major are all in roughly the same patch of sky. Each is made up of enough first- and second-magnitude stars that they are visible even from light-polluted locations; the three stars marking Orion’s belt are obvious even in cities like New York, Paris or Chicago. By 6 p.m. on Jan. 6 the full moon is rising in the east, and to the south of it (on the right) one can see Orion’s Belt, which will be almost vertical. Looking almost straight up from the moon (and after allowing one’s eyes to adjust, as the moon is very bright) one can see Capella, the brightest star in Auriga, the Charioteer. To the right will be Mars (recognizable because of its reddish color) and right below and to its right is Aldebaran, the brightest star in Taurus. Since the moon will be in Gemini, the constellation’s two brightest stars, Castor and Pollux, will be just to its right (and above it later in the evening as the moon gets higher).
In the Southern Hemisphere, the summer stars are high in the early evening; in mid-southern latitudes (as in, for example, Santiago, Chile, Melbourne, or Cape Town) the constellations that make up the legendary ship of Jason, the Argo, are high in the southeastern sky by 10 p.m. local time. The three constellations are Carina, the keel, Puppis, the deck, and Vela, the sail. The brightest star among them is Canopus, which will be to the right of Sirius as one faces roughly south. Further west (right) one can see Achernar, the star that marks the end of the River, Eridanus, and if one follows the trail of stars that makes up the river’s course one ends up near an “upside down” Orion.
The January full moon is often called the Wolf Moon, according to the Old Farmer’s Almanac, which may date back to Native American tribes and early Colonial times when wolves would howl outside villages.