January Super Wolf Blood Moon: Total Lunar Eclipse Will Be Last Until 2021

blood moon
A blood moon seen from Australia in July, 2018. WILLIAM WEST/AFP/Getty Images

On the night of January 20, there will be a rare celestial event—a lunar eclipse will coincide with the Moon at perigee. The lunar eclipse, also known as a "blood moon" because of the reddish hue it displays, will take place at the same time as the full moon's close approach to Earth.

At this point, the Moon appears slightly bigger than normal, earning it the name "supermoon." As a result, January's full moon will be a super blood moon.

The full moon in January is also known as a full wolf moon, according to The Old Farmer's Almanac. This is because it heralded a period when wolves would howl with hunger outside villages.

Read more: Super blood moon is coming—total solar eclipse and supermoon converging explained

Walter Freeman, assistant teaching professor in the Physics Department at New York's Syracuse University, said people wanting to see the lunar eclipse should start looking from around 10.35 p.m. ET. "At that time, the Earth's shadow will begin to pass in front of the Moon, blocking almost all of the Sun's light from reaching it," he said in a statement.

"Observers will see the Moon appear to be progressively 'swallowed up' starting from the lower left. This process will end at 11:40 p.m., when the Earth's shadow covers the whole of the Moon's surface; this is the beginning of 'totality.' This will last until around 12:40 a.m., when the motion of the Earth's shadow will carry it past the Moon, and the Moon will gradually again be lit by the Sun. At 1:45 a.m., the Moon will be fully visible again."

A lunar eclipse occurs when the Moon passes directly through the Earth's shadow. When this happens, most of the light from the Sun is blocked by Earth, but some is refracted through the atmosphere, allowing it to hit the surface of the moon. The angle at which the light is bent produces the reddish tint of a blood moon.

Lunar eclipses are fairly rare—with less than one per year on average, Freeman said. "Partial solar eclipses—where the Earth's shadow doesn't completely cover the Moon, and only takes a bite out of the side of it—are more common."

The next total lunar eclipse will take place on May 26, 2021, and this will be visible for a large part of North America. The next one after that will be May 15, 2022.

Lunar eclipses coinciding with a supermoon are rare. Over the 21st century, there will be 87 total lunar eclipses. Of these, only 28 will coincide with a supermoon, Anna Ross, an astronomer at the Royal Observatory Greenwich, London, told Newsweek.

For viewers of the January lunar eclipse, Freeman said no precautions need to be taken: "A blood moon is one of the few opportunities we have to see both the Moon and the stars in the sky at the same time, since the Moon is usually too bright."