PSA: Super Blood Wolf Moon Eclipse
That’s a mouthful, but let’s break it down. January’s full moon is a supermoon, meaning that the moon is at the point in its orbit where it is nearest to Earth. This is called perigee. The average distance from Earth to the moon is 238,855 miles (384,400 kilometers). At perigee this January, the distance will shrink to 222,043 miles (357,344 km). At the moon’s next apogee in February, when the moon is farthest from Earth, it will be 252,622 miles (406,555 km) away from Earth.
Practically speaking, perigee is hard to detect with the naked eye. As the editor of Sky & Telescope magazine Alan MacRobert noted in advance of a 2016 supermoon, the moon looks about 25 percent brighter and around 15 percent greater in area at perigee — “not enough to notice unless you’re a very careful moon-watcher,” he said. [Here’s How to Watch Sunday’s Lunar Eclipse]
Blood and wolves
The “wolf” part of this month’s moon moniker is simply a reference to the month of January. According to the Farmers’ Almanac, each month’s full moon has a name, supposedly cobbled together from traditional Native American or old Anglo-Saxon names. No one knows the precise origin of “wolf moon,” but that’s the name typically assigned to January. [Photos: The Adventure Behind Eclipse Chasing]
The rest of the name is all about planetary geometry. This month, as the moon swings closest to Earth, the moon will also undergo a total lunar eclipse. Lunar eclipses happen when Earth is between the sun and the moon, and the moon passes into Earth’s shadow.
“Not just any part of the shadow,” said Paul Hayne, an astrophysicist at the University of Colorado Boulder, “but the deepest, darkest part of the shadow, called the umbra.”
Despite the moon’s position in this deep shadow, it won’t entirely vanish from Earthlings’ sight. A little bit of sunlight sneaks through Earth’s atmosphere, bent and scattered by the thin sheen of gases blanketing our planet. Red wavelengths of light pass through, creating an eerie vermilion hue on the moon’s face for viewers on Earth. From the moon, it would look as if Earth were surrounded by an orange ring of fire.
“It’s like seeing a sunset all the way around the Earth,” Hayne told Live Science. Because of the color, lunar eclipses are also known as “blood moons.”
The total eclipse of the moon will last an hour and 2 minutes, according to NASA, with the partial phase stretching out over 2 hours and 17 minutes. The show starts subtly at 9:36 p.m. EST (6:36 p.m. PST) with a penumbral eclipse, when the outer edge of Earth’s shadow will very slightly darken the moon’s face. 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 Earth’s shadow, the umbra. This marks the start 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 entirely within the umbra, and the whole surface should appear dusky 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, subtle darkening of the penumbral eclipse will pass at 2:48 a.m. EST (11:48 p.m. PST). Weather permitting, most of the United States — except for Hawaii and some of the Aleutian Islands — will have a great view, Hayne said.