ORONO, Maine — The ‘supermoon’ summer is on its way, with full moons in July, August and September looking larger than normal.

This will especially be the case when the moon is rising, because it occurs when the moon is at or near its closest orbital point to Earth, according to Alan Davenport, director of Jordan Planetarium at the University of Maine. Hence the term supermoon.

“The moon’s orbit is an elliptical one — it’s not a circle — so it’s constantly moving closer and further away from us,” Davenport said Friday. “The supermoon cycle only occurs when you have both a full moon and at the same time you have a perigee — that is where it’s closest to the Earth in its orbit.”

According to NASA’s Science website, when the moon is at the perigee of its orbit, it is about 31,000 miles closer to the Earth than when it is at the furthest orbital distance, called the apogee. That’s why full moons that occur on the perigee seem extra big and bright.

The full moon-perigee coincidence happens three times in 2014, according to NASA. On July 12 and Sept. 9 the moon will become full the same day as its perigee. On Aug. 10 it will become full during the same hour as perigee, according to the NASA site.

The July full moon will rise Saturday at about 8:14 p.m. in Maine. But people who look at the sky Friday, when the moon is nearly full, also should see the supermoon effect, Davenport said.

“It’s a cool mathematical event,” he said.

Geoff Chester of the U.S. Naval Observatory told NASA that supermoons are not rare.

“Generally speaking, full moons occur near perigee every 13 months and 18 days, so it’s not all that unusual,” he said. “In fact, just last year there were three perigee moons in a row, but only one was widely reported.”

The June 2013 moon was reported as 14 percent bigger and 30 percent brighter than other full moons last year, according to NASA.

How do you celebrate a supermoon?

There are supermoon paddles planned at the Hirundo Wildlife Refuge in Alton for next month and for September to watch the moon rising above the wetlands, a press release about the events states. Those interested in finding out more can call 394-2171 or check out the group’s website at hirundomaine.org.