The Reason We Sometimes See a Ring around the Moon

Where did that ring around the moon come from?

The reason we sometimes see a ring around the moon
March 7, 2018

Unexpected beauty

It’s not often that running out to grab something you left inside your car turns into a beautiful experience. In fact, that had never happened to me—until last week.

As I walked out to the car I happened to look up at the moon. It was an incredibly clear night. The stars were shining and beautiful. The moon was breathtakingly large, bright and there was a huge ring around it. Unfortunately, the photo I took doesn’t do justice to what I saw. But I stopped and marveled at how pretty it all was. And then I wondered, what caused it? Was the moon suddenly jealous of Saturn and its rings?

Ring Caused By Refracted Moonlight

It turns out that ring is caused by the refracting (or bending) of moonlight through ice crystals that are suspended in the upper atmosphere. We’re talking really upper atmosphere: about five to ten kilometers or roughly five to six miles high.

The National Weather Service also says it doesn’t have to be winter to witness this amazing site because below freezing temperatures exist at high altitudes any time of the year. Those ice crystals usually make up cirrus clouds—the wispy, thin clouds that are found really high up in the sky.

And that plays into an old saying I remembered my grandparents telling me, “ring around the moon means rain is coming soon.” High cirrus cloud are often seen a day or two before low-pressure systems arrive over an area. Low-pressure systems often do bring precipitation. Good thing I cut the grass!

—Frank Graff 

Frank Graff is a producer/reporter with UNC-TV, focusing on Sci Tech Now North Carolina, a weekly science series that airs Tuesdays on UNC-TV. In addition to producing these special segments, Frank will provide additional information related to his stories through this North Carolina Science Now Reporter's Blog!