Tonight’s moon will simultaneously be full, super and blue

Full moon, supermoon, blue moon — Monday night’s sky will have all three types rolled into one.

The rare spectacle, not to be seen again for another 13 years, happens when the moon is full, and different cycles of blue and super moons align on the calendar. Astronomers’ varying definitions for each type of moon also play a role in bringing the combination about.

But for skywatchers, the bottom line is they are in for a treat as a big and bright moon will grace the night sky on Monday and Tuesday nights.

“It’s going to be incredible,” said Thaddeus LaCoursiere, the planetarium production coordinator at the University of Minnesota’s Bell Museum. “With clear skies, it will be hard to miss.”

For starters, LaCoursiere said the full moon won’t actually turn blue, despite being referenced as a blue moon. A full moon appears about once a month. But because the moon orbits Earth in about 29 days, there are occasions when there are two full moons in a month. Since the 1940s, the term blue moon has been used when a second full moon occurs in the same month.

Not as widely known, the term also applies when there is a third full moon within the same season that will have four of them. While Monday’s full moon is the only one in August, it is the third this summer, qualifying it as a blue moon, according to LaCoursiere.

A supermoon occurs when the moon’s orbit is closest to Earth at the same time that the moon is full. The term was coined in 1979 by astrologer Richard Nolle to describe the moon’s close approach to Earth. The moon’s orbit is in somewhat of an oval, so its distance from Earth fluxuates. Tonight, the moon will be about 224,000 miles from Earth, much closer than the more than 250,000 miles when it is furthest away.

The moon will be even closer during September’s supermoon, at about 220,000 miles, LaCoursiere said.

As the moon gets closer to Earth, supermoons “are the biggest and brightest full Moons of the year,” NASA said. The moon can appear about 14% bigger and up to 30% brighter than normal, the agency said.

The full moon will be at its peak at 1:26 p.m. CDT Monday, NASA said, but it won’t be very visible during the daylight hours. As the moon moves away, it will slowly shrink. By evening, those in the Twin Cities will see 99.7% of the moon, LaCoursiere said.

The confluence of all three types of moons is “uncommonly common,” he added. The last time all three phases aligned was in 2017 and isn’t predicted to happen again until 2037.

For prime viewing, simply look up, LaCoursiere said.

“You don’t need to leave the city,” and you don’t need binoculars or a telescope, he said. “You can see it with your own eyes.”

Three more supermoons are coming this year, with the full moons in September and October tying for coming closest to Earth, NASA said. In addition, the full and supermoon coinciding on Oct. 17 will feature a partial lunar eclipse, NASA said.