The moon acquires a red hue as it slides into the shadow of the Earth during a total lunar eclipse.
Credit: CHEN HSI FU / Shutterstock
Come to work late on Monday (January 21) and get ready to spend Sunday night looking at the sky: the eclipse of the Super Blood Moon Wolf is coming.
That's a mouthful, but let's break it down. The full moon of January is a supermoon, which means that the moon is at the point in its orbit where it is closest to Earth. This is called perigee. The average distance from Earth to the Moon is 238,855 miles (384,400 kilometers). In the perigee of this month of January, the distance will be reduced to 222,043 miles (357.344 km). At the next peak of the moon in February, when the moon is farthest from Earth, it will be 252,622 miles (406,555 km) from Earth.
In practical terms, the perigee is difficult to detect at a glance. As the editor of Sky & Telescope magazine Alan MacRobert pointed out before a 2016 supermoon, the moon looks 25 percent brighter and 15 percent larger in the perigee area – "it's not enough to notice unless you are a very careful observer of the moon, "he said. [Here’s How to Watch Sunday’s Lunar Eclipse]
Blood and wolves
The "wolf" part of this month's moon nickname is simply a reference to the month of January. According to the Farmers' Almanac, the full moon of each month has a name, supposedly improvised with the names of traditional Native Americans or ancient Anglo-Saxons. No one knows the precise origin of the "wolf moon", but that is the name that is typically badigned to January. [Photos: The Adventure Behind Eclipse Chasing]
The rest of the name has to do with planetary geometry. This month, when the moon oscillates closer to Earth, the moon will also experience a total lunar eclipse. Lunar eclipses occur when the Earth is between the sun and the moon, and the moon pbades in the shadow of the Earth.
"Not any part of the shadow," said Paul Hayne, an astrophysicist at the University of Colorado Boulder, "but the deepest and darkest part of the shadow, called the umbra."
Despite the position of the moon in this deep shadow, it will not disappear completely from the sight of the earthlings. A little bit of sunlight sneaks through Earth's atmosphere, bent and scattered by the fine glow of the gases that cover our planet. The red wavelengths of light pbad through them, creating a strange vermilion tone on the face of the moon for Earth viewers. From the moon, it would seem that the Earth was surrounded by an orange ring of fire.
"It's like watching a sunset around the Earth," Hayne told Live Science. Due to color, lunar eclipses are also known as "blood moons".
Where to look
The total eclipse of the moon will last one hour and 2 minutes, according to NASA, and the partial phase will last for 2 hours and 17 minutes. The show begins subtly at 9:36 p.m. EST (6:36 p.m. PST) with a penumbral eclipse, when the outer edge of the shadow of the Earth will slightly darken the face of the moon. Things will get a little more interesting around 10:34 p.m. EST (7:34 PST), when the moon enters the main, darker portion of the shadow of the Earth, the umbra. This marks the beginning of the partial lunar eclipse.
At 11:41 p.m. EST (8:41 PST), the total eclipse begins. At this point, the moon will be completely inside the umbra, and the entire surface should appear dark red. The total eclipse will last until 12:43 a.m. EST (9:43 p.m. PST), and the partial eclipse will end at 1:51 a.m. EST (10:51 p.m. PST). The final and subtle darkening of the penumbral eclipse will happen at 2:48 a.m. EST (11:48 p.m. PST). If the weather permits, most of the United States, except Hawaii and some of the Aleutian Islands, will have a great view, Hayne said.
"The next total eclipse will not be until 2021 in May, and there will not be as good visibility in the US for that," he said.
Hayne will be watching the eclipse from a little perfect perch in Hawaii, where the moon will not come out until much of the show is over. He and his fellow scientists will see the eclipse using a thermal infrared camera at an observatory there. When the moon pbades into the shadow of Earth, says Hayne, it begins to cool. The different materials are cooled at different speeds, so the infrared view allows the researchers to see features of the surface that are generally difficult to discern.
"In fact, we can see how the youngest impact craters on the surface of the moon go crazy when the moon goes into an eclipse," Hayne said.
Originally published in Live Science.