The full moon of January, called the Wolf Moon, will occur on Jan. 10 at 2:21 p.m. EST (1921 GMT), and it will coincide with a lunar eclipse for skywatchers in much of the world.

During this eclipse, the moon will pass through Earth's faint outer shadow, called the penumbra. The shadow will give the moon's face a tea-stained color for about 4 hours, beginning at 12:07 p.m. EST (1707 GMT), with maximum eclipse occurring at 2:10 p.m. EST (1910 GMT). The eclipse will be visible everywhere except from the United States, central Canada, a majority of South America and Antarctica.

The full moon happens about once every 27 days, when the moon and the sun are on exactly opposite sides of Earth. 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 from Earth.

Related: How Lunar Eclipses Work (Infographic)

The time of the full moon is the same everywhere, since it is determined by where the moon is relative to Earth rather than its apparent position in the sky, which is slightly different, depending on one's location. In accordance with local times, observers in the British Isles and Portugal will see the moon become full at 7:21 p.m., while those in western continental Europe will see it at 8:21 p.m., and skywatchers on the east coast of Australia will see it at 5:21 a.m. on Jan. 11. In New York City, the moon will rise at 4:45 p.m. local time, according to timanddate.com. The moon will be in the constellation Gemini and will rise about 2 minutes before sunset.

As the moon is on the opposite side of Earth from the sun, one would expect that it would pass through Earth's shadow. Because the plane of the moon's orbit around Earth is tilted, however, lunar eclipses do not happen every time the moon is full.

The penumbral lunar eclipse on Jan. 10 will be the first of four lunar eclipses happening in 2020; the next three will also be of the penumbral type. A penumbral eclipse doesn't darken the moon nearly as much as a total lunar eclipse, also known as a blood moon. During a total lunar eclipse, the moon passes through the inner part of Earth's shadow (called the umbra). As the light from the sun is refracted through Earth's atmosphere, it darkens until it turns a reddish color.

A visibility map for the penumbral lunar eclipse of Jan. 10, 2020. (Image credit: Fred Espenak/NASA)

A penumbral eclipse can be difficult to notice with the naked eye. Keen-eyed observers might see the moon turn from white to slightly yellowish on a perfectly clear night, and in this event, about 89% of the moon's face will be covered by the penumbra. If you want to try and see it, you need to be where the moon is above the horizon when it touches Earth's shadow, which will be in Europe, Africa, Asia and the far northeastern and northwestern regions of North America.

In London, for example, the moon will touch Earth's shadow at 5:08 p.m. and exit at 9:12 p.m. local time. In New Delhi, the eclipse begins at 10:38 p.m. local time Jan. 10 and ends at 2:42 a.m. Jan. 11. In Melbourne, Australia, the eclipse starts on Jan. 11 at 4:08 a.m. local time, but the moon sets at 6:10 a.m., just before maximum eclipse, according to skywatching site In-The-Sky.org.

Related: Amazing Photos of the Super Blood Wolf Moon of January 2019

Since the full moon is on the opposite side of Earth from the sun, Northern Hemisphere observers will see it relatively high in the sky — essentially the moon is where the sun would be in the summer months. From New York City, this means the moon hits a maximum altitude of about 71 degrees; observers just a bit farther south in Miami, Florida, will see it reach 87 degrees — nearly straight up at the zenith at local midnight. In the Southern Hemisphere, the reverse is true, as it is summer there. In Cape Town, South Africa, the full moon will reach a maximum altitude of only 32 degrees at 12:03 a.m. local time on Jan. 11.

Visible planets and constellations

Northern Hemisphere skies are full of bright constellations — 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 Paris.

On the night of the full moon, two planets will also be apparent. In New York, just as the moon rises in the east, Venus will be in the western sky; the planet sets at 7:42 p.m. local time. Mars, meanwhile, rises at 4:04 a.m. on Jan. 11, while the moon sets at 8:07 a.m. (sunrise is at 7:19 a.m. local time).

Jupiter and Saturn are both close to the sun in the sky; Jupiter rises on Jan. 11 at 6:39 a.m. local time in New York, and Saturn sets on Jan. 10, only 6 minutes after the sun does. Jupiter will be only 6.4 degrees above the horizon at sunrise, according to heavens-above.com calculations.

(Image credit: Shutterstock)

The Wolf Moon

The January full moon is often called the Wolf Moon, according to the Old Farmer's Almanac, and the name 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 Anishinaabe) peoples called it Mnido Giizis, the Spirit Moon, marking a time of prayer and contemplation. The Tlingit of the Pacific Northwest call the January full moon T'awaak Dís, or Goose Moon, while the Haida called it Táan Kungáay, or "Bear hunting moon," according to the Tlingit Moon and Tide Teaching Resource published by the University of Alaska at Fairbanks.

In China, the traditional lunar calendar calls this full moon lunation the 12th month, Làyuè , or Preserved Month, named for the practice of preserving meats during the winter.

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