The full moon Friday night into Saturday will appear to be unusually big. In fact, it will be a “supermoon.”

That’s the nickname for full moons that happen when our celestial neighbor is relatively close to Earth. That distance varies because the moon follows an elliptical orbit. When it’s close and full, it appears bigger and brighter than normal, although in fact the difference can be hard to detect.

If you see Saturday’s moon close to the horizon it may seem huge, but that’s just an illusion caused by its position in the sky.

(In Hawaii, the moon rises at 6:47 p.m. Friday night and sets at 5:14 a.m. Saturday. The full moon reaches its crest at 1:25 a.m.)

Two other full moons this summer, on Aug. 10 and Sept. 9, are also supermoons.

It’s not all that unusual to have a supermoon. There were three in a row last year.

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Online:

NASA on supermoons: http://1.usa.gov/1jxZkPt