On average, the moon orbits at a distance of about 238,000 miles from Earth. But at perigee, it’s about 226,000 miles away — or about 12,000 miles closer to Earth. So if the moon is full at this point, it appears up to 30 percent brighter and up to 14 percent larger than a full moon that occurs when the moon is at its most distant point from Earth in its elliptical orbit. That point is known as lunar apogee.
The term supermoon was coined by an astrologer, and not all astronomers are comfortable with it. Neil deGrasse Tyson, director of the Hayden Planetarium at the American Museum of Natural History in New York City, said in a 2017 tweet that “the very concept of a Super Moon is an embarrassment to everything else we call super: Supernova, Supercollider, Superman, Super Mario Bros.”
And as Penn State University astronomer Christopher Palma wrote in 2016, "As an observational astronomer who teaches students about the behavior of the moon, I’m thankful for anything that inspires people to go out and look at the sky.”