- Because the moon travels an elliptical path, it sometimes gets a little closer to Earth and appears larger in the night sky.
- This "supermoon" moment is called perigee.
- During that time, up to 30% more moonlight is showered on us, according to NASA.
This Sunday is your chance to get up close and personal with the moon.
The year's only visible supermoon (or perigee-syzygy, if you prefer the technical term) happens on December 3, meaning the moon, which traces an elliptical orbit around the Earth, will come as close to us as it gets. At that point, it may appear a little bigger and brighter than usual.
According to NASA, when the moon is in that perigee position, it can be up to 14% closer to us than it is at apogee — its farthest distance from our planet, also known as the micromoon.
It can also shine up to 30% more moonlight on the Earth, NASA says.
The supermoon can also cause stronger tides and influence the Earth's weather.
Photos of the November 2016 supermoon elicited oohs and aahs in clear skies from Beijing to Baikonur, Kazakhstan.
This Sunday's show may not be quite that impressive, though. The previous supermoon was the closest to Earth since 1948, and we won't see another like that until 2034.
In fact, Jackie Faherty, an astrophysicist at the American Museum of Natural History, predicts that many people won't even notice this weekend's supermoon.
"To the untrained eye, the moon will look no different," Faherty told Business Insider in an email. "Even for the trained eye, it will not be anything to speak of."
But she shared a few tips for those interested in checking it out and snapping some pictures.
When to watch
The full supermoon won't technically hit the US until Monday morning (12:45 a.m. PT, 3:45 a.m. ET), but most of the best moon photo ops happen around moonrise and moonset — that'll be around 5 p.m. ET on Saturday and 7:50 a.m. ET on Sunday.
During moonrise, "you will experience the optical illusion which makes the moon appear larger when viewed against the horizon," Faherty said.
It can be tough to snap a good shot of the moon, but equipment like a telephoto lens or an adapter on a small telescope helps, Faherty said. And if you can get near water, the reflection of the lunar light will make the phenomenon even more dramatic.