A perigee moon, also known as a 'supermoon,' rises over a crescent of a minaret of grand Faisal mosque in Islamabad, Pakistan, Saturday. (Anjum Naveed/The Associated Press)
The full moon on 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 neighbour 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.
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.
