The moon might look a bit bigger Saturday night -- particularly if you look while it is hanging low in the sky.
The phenomenon is caused when the moon is at its perigee (its closest point to the Earth) at the same time it is full.
The last time this occurred was March 8, 1993, according to Geoff Chester, an astronomer and public information officer at the U.S. Naval Observatory.
"It's important because it's something that happens once every 18 years," Chester said. "But it's not as if the Earth is going to fall off its axis. There's no reason to get in a lather."
Terry Bienstock, president of the Montauk Observatory, said that though the moon would look slightly bigger, it was actually not a good night to view it. "When the moon is only partly visible you can see the shading and the craters much better," Bienstock said.
Despite what Chester called the "hoo-ha" that surrounds these "supermoons," as they're sometimes called, it was also an opportunity to study humans' emotional connections to the moon.
"The first known images drawn by man, probably with bones, are of the moon," Chester said. "And there was once a time when every farmer knew the names of every moon in every month."