Clouds over Launch Complex 39 at NASA's Kennedy Space Center threaten to obscure the view of the supermoon forecast to light up the sky.

Clouds over Launch Complex 39 at NASA’s Kennedy Space Center in Florida threaten to obscure the view of the “supermoon” forecast to light up the sky.

The scientific term for the supermoon phenomenon is "perigee moon." Full moons vary in size because of the oval shape of the moon's orbit. The moon follows an elliptical path around Earth with one side about 50,000 kilometers closer than the other. Full moons that occur on the perigee side of the moon's orbit seem extra big and bright. For additional information, visit http://science.nasa.gov/science-news/science-at-nasa/2014/10jul_supermoons/. Photo credit: NASA/Ben Smegelsky