January full moon 2021: The ‘Wolf Moon’ rises with winter constellations

The full moon of January, called the Wolf Moon, will occur on Thursday, Jan. 28, at 2:16 p.m. EST (1916 GMT) according to NASA. The moon will be in the constellation Cancer, and rises just a few minutes before sunset.

Full moons happen when the moon is exactly on the opposite side of the Earth from the sun, so the entire Earth-facing side is illuminated. As it happens the rotation period of the moon is the same as its orbital period, so we always see the same side of our satellite. (This gives rise to another misnomer, the “dark side” of the moon. Both sides of the moon get the same amount of light, the far side of the moon is just one we don’t happen to see from Earth).

The timing of the full moon is the same everywhere — though the hour depends on your time zone. That’s because it is determined by the moon‘s position relative to the Earth rather than its apparent position in the sky, which differs slightly depending on your location. So while the moon is officially full at 2:16 p.m. in New York, that will be 6:16 a.m. on Jan. 29 in Melbourne. To catch the actual moment of the full moon while it is above the horizon, one needs to be east of New York City — in London, for example, the moon is full at 7:16 p.m., after the sun sets at 4:43 p.m. Similarly in Paris, the full moon will be later, at 8:16 p.m.

Given that the full moon is roughly on the opposite side of the sky as the sun, for Northern Hemisphere observers the moon in winter appears high, just as the sun would be in the summer months. From New York this means the moon hits a maximum altitude of about 72 degrees on Jan. 28; observers just a bit further south in Houston will see it reach 83 degrees — nearly the zenith at local midnight. For Southern Hemisphere observers the reverse is true, as it is summer there. In Santiago, Chile, the full moon will reach a maximum altitude of only 32.5 degrees at 1:29 a.m. local time on Jan. 28.

An interesting phenomenon is when the full moon is visible in the sky before sunset. This occurs in the winter months, as the nights are longer, and even though the sun and moon are 180 degrees apart, the length of night is longer than 12 hours. So in New York, where the day is about 10 hours long on Jan. 28, the moon rises before sunset. This effect is more pronounced the further north you go; from London (which is 10 degrees farther up in latitude) the day length is just under 9 hours, and the full moon rises at 4:09 p.m., a full 34 minutes before sunset. Going farther north, to Reykjavik, the moon rises at 3:51 p.m. local time, and the sun doesn’t set until 5:02 p.m.

Visible planets

This sky map shows the Full Wolf Moon with planets and constellations as seen from New York City, on Jan. 28, 2021, at 8 p.m. local time. (Image credit: SkySafari app)

Beyond the full moon, observers can check for visible planets, which are bright enough that the full moon doesn’t wash them out. On Jan. 28, Mercury, usually difficult to observe, will be at an altitude of 14 degrees when the sun sets in New York, and should become visible about a half hour after sunset, when it will be about 10 degrees high — approximately the width of a fist at arm’s length. Per Heavens-Above.com calculations the planet sets over New York at about 6:32 p.m. local time.

Venus, meanwhile, is still a “morning star,” but it rises in New York only about 40 minutes before sunrise, at 6:31 a.m. local time. That means the planet won’t gain much altitude by the time the sky gets light; by 6:45 a.m. it will be about 2 degrees in altitude, only visible if you have a very flat horizon (for example, looking out over the ocean or flat plain) and a clear sky.

Farther south observing gets easier. From San Juan, Puerto Rico, where the sun rises at 6:58 a.m. on Jan. 28, Venus rises at 6:09 a.m., which means that by about 6:30 it will be 4 degrees high — still challenging, but Venus’ brightness can help. From cities near the Equator, such as Quito, Venus will reach about 8 degrees a half-hour before sunrise (which is at 6:23 a.m. at that latitude).

While the Great Conjunction is behind us, Jupiter and Saturn are still relatively close to each other, but both are now so close to the sun that seeing them is not possible. In fact, Jupiter is in conjunction with the sun on Jan. 28, meaning the planet will pass behind the sun from Earth’s point of view. It will emerge in the predawn sky in the coming weeks. Saturn has already taken its place west of the sun; it rises on Jan. 28 at 7:03 a.m. in New York, so it’s basically invisible. Saturn also will emerge from the sun’s glare as the year progresses.

Mars, meanwhile, stays visible throughout the first half of the evening. As the sun sets and the full moon rises, Mars will be about halfway between them; in New York it reaches its maximum altitude of 65 degrees at 5:54 p.m. on Jan. 28 and sets at 12:51 a.m. on Jan. 29. In the constellation Aries, it’s classic red color and relative brightness makes it easy to spot from even a light-polluted city.

Stars and constellations

Northern Hemisphere skies are full of bright stars — the constellations of 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 or Los Angeles.

The southern latitudes also have some famous constellations (and bright stars) during their summer months. From mid-southern latitudes by about 8 p.m. in your local time, you can see not only Orion, Canis Major and Taurus (they will be “upside down” and to the north) but also Carina, Vela and Puppis, the three constellations that are traditionally associated with Argo Navis, the ship of Jason.

Canopus is the brightest star in Carina and the second-brightest star in the sky. Looking just below Canopus one can see the constellation of Centaurus, the centaur (home of Alpha Centauri, the closest star to our solar system) and the Southern Cross. A Southern Hemisphere skywatcher can also trace Eridanus, the river, from its beginning near the “foot” of Orion (the star Rigel) all the way towards the west to its end at the star called Achernar, known for being the least spherical star in the sky as it rotates so fast that it is flattened.

The Wolf Moon

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.

According to the Ontario Native Literacy Project, the Ojibwe (or Aanishnabeg) peoples called it Mnido Giizis, the Spirit Moon, marking a time of prayer and contemplation. Among the Cree peoples it was sometimes called Opawahcikanasis, the Frost Exploding Moon — for the sound of trees crackling from the winter frost common in many parts of Canada.

The Māori of New Zealand measured lunar months between new moons, so the full moon of January falls in the middle of the month called Hui-tanguru, or “The foot of Rūhī (a summer star) now rests upon the earth.” Rūhī refers to a star in Scorpio, near Antares. During the austral summer Scorpio tends to be below the horizon until after midnight.

In China, the full moon will fall in the 12th month of the traditional lunar calendar, Làyuè, or “Preserved Month” which refers to preserving foods for the spring festivals.

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