From the first total solar eclipse to grace the continental United States in nearly 40 years to the recent Leonids meteor shower, we earthlings have been spoiled with a regular collection of astronomical events this 2017. And although the year may be coming to an end, the awe-inspiring events just kept coming over the weekend. Recently, skywatchers had the opportunity to take in a rare supermoon overhead — the first and last supermoon of this year. Above, we curated a list of some of the best supermoon photos snapped around the globe but what exactly is a supermoon?

Rather than a perfect circle, the moon orbits around our home planet in an elliptical pattern and one full orbit around our planet takes roughly 29.5 days. Depending on the moon’s location on this elongated orbital trajectory, our faithful natural satellite is sometimes closer or farther away from our planet. At the closest point of this orbit (perigee), the moon is a more than 31,000 miles closer to our planet than it is during its farthest point of orbit (apogee).

Similarly, as most of us well know, the moon drifts through a sequential set of phases as it orbits our planet: Full, crescent, waxing, and waning gibbous. (NASA’s so-called “Dial-a-Moon” feature allows individuals to easily track and predict this shifting phases.) A “supermoon’ occurs when we observe a full moon during or near its perigee. Sunday’s supermoon appeared specifically 16 percent brighter and seven percent larger than the moon normally does. Per Jim Lattis, an astronomer at the University of Wisconsin-Madison, this celestial treat occurs roughly once every 14 full moons.