Supermoon, Blue Moon and Lunar Eclipse Lights Up the Sky Next Week

Skywatchers will get a rare triple treat January 31, 2018 as a supermoon, a blue moon and a total lunar eclipse happen all in one week.

How rare is the event? Even without the supermoon, it’s the first blue moon total lunar eclipse in the U.S. since March 1866, less than a year after the Civil War ended, according to EarthSky.org.

A blue moon — which occurs about every 2½ years - is another term for the second full moon in a single calendar month. January’s first full moon occurred Jan. 1.

Though the exact moment of this full moon is 8:37 a.m. ET Jan. 31, the moon will appear plenty full for a day or two before and after that. However, keep in mind, the moon doesn’t actually appear blue.

As for the total lunar eclipse, it will be visible early in the morning of January 31 from western North America across the Pacific to eastern Asia according to NASA.

In the United States, the best view of the eclipse will be along the West Coast. For skywatchers in the central and eastern U.S., only a partial eclipse will be visible since the moon will set before totality.

“The lunar eclipse on Jan. 31 will be visible during moonset,” said Noah Petro, a research scientist from NASA’s Goddard Space Flight Center. “Folks in the eastern United States, where the eclipse will be partial, will have to get up in the morning to see it.”

The real star of the show for moon watchers is the lunar eclipse on Jan. 31. The supermoon (when the moon reaches its closest point to Earth in this orbit) will be the day before, on Jan. 30 at 4:58 a.m. EST (0958 GMT). The moon will be 223,068 miles (358,994 kilometers) from Earth, compared to the average distance of 238,855 miles (384,400 km), according to NASA.

Though a supermoon does appear slightly larger in the sky than a full moon that takes place when Earth’s lunar companion is farther away from us in its orbit, the difference is nearly impossible for most skywatchers to notice because the moon is so bright and the maximum possible difference in the moon’s apparent size is small (only about 14 percent), according to NASA.

Unlike solar eclipses, which are only visible from specific places on Earth, lunar eclipses are visible from anywhere it is nighttime. Lunar eclipses don’t occur every month because the plane of the lunar orbit is slightly tilted relative to the plane of the Earth’s orbit, so the Earth, sun and moon don’t always line up to put the moon in Earth’s shadow. For the Jan. 31 lunar eclipse, viewers in some places will not be able to see the entire event because it starts near moonrise or moonset. Lunar eclipses are only visible on Earth’s night side.

To see as much of the eclipse as possible, you’ll want to be near a flat western horizon. In Denver and points west, the eclipse will start at 3:51 a.m. local time, with the umbra reaching the moon’s edge at 4:48 a.m. Californians will have a better view of the end of totality, as the penumbral eclipse will start at 2:51 a.m. local time, and the partial eclipse will begin at 3:48 a.m. As one travels west across the Pacific, the lunar eclipse will occur earlier in the night; skywatchers in Hawaii will be able to see the entire thing from beginning to end, as will Alaskans and viewers in eastern Asia and Australia.

The full moon will take on a dark, reddish appearance during the eclipse, so another phrase used to describe it is a blood moon. Adding to the naming confusion, this full moon was also known as the “snow moon” by some Native American tribes.

Finally, a supermoon occurs when the full moon is at the closest point of its orbit to the Earth, which is also called the perigee.

That makes the moon look extra-close and extra bright — up to 14% bigger and 30% brighter than a full moon at its farthest point from Earth, known as the apogee, NASA said.

Information provided by NASA and Space.com.