A slightly larger, brighter full moon will appear in the sky Sunday night.

On Sunday, December 3, the full moon will appear slightly larger and brighter than normal in the sky when it rises in the early evening. It will be the last (and only) “supermoon” of the year. And while it’s not as spectacular of an event as a solar or lunar eclipse, it’s as good of a reason as any to step outside Sunday night and get a close look at Earth’s natural satellite.

What is a supermoon? Why does it happen? And is it all that special?


The moon’s orbit around Earth is not a perfect circle. It’s an ellipse, a saucer shape that’s longer than it is wide. That means as the moon follows this orbit, it’s sometimes closer to the Earth and sometimes farther away. At perigee, the closest spot in its orbit to the Earth, it’s around 31,068 miles closer to Earth than at apogee, when it’s farthest away.


Meanwhile, we see different phases of the moon — full, crescent, waxing, and waning gibbous — depending on if the sun-facing side of the moon is facing the Earth.

 Ernie Wright/NASA

A supermoon is when these two cycles match up, and we have a full moon that’s near its perigee. The result is that the full “super” moon appears slightly larger and slightly brighter to us in the sky. This occurs about one in every 14 full moons, Jim Lattis, an astronomer at the University of Wisconsin Madison, notes.

The supermoon doesn’t have any astronomical significance other than it makes for a slightly larger target for backyard astronomers to look at. In fact, the term Read More Here