MOLINE, Illinois — Recently, the full moon took on a neat appearance, which several of you noticed. Connie from Alton, Illinois, sent us this picture of the moon that appeared to have a halo surrounding it. So, what caused this unique appearance?
It all has to do with something we can and can’t see… water vapor!
The night of the ring, we had a very thin layer of cirrus clouds located high up in the atmosphere. This layer was thin enough to remain mostly invisible to us here at the ground, but thick enough to provide plenty of water particles for the moonlight to reflect upon. The appearance is known as a lunar (moon) halo.
Lunar halos are neat because they form using the same process that creates sun halos during the day. There’s an old saying relating to this phenomenon: ring around the moon means rain soon. This is almost always true because high cirrus clouds are almost always tied to distant storm systems. These clouds often drift as high as 20,000 feet above us! Within these clouds are millions of tiny ice crystals that will refract light from the moon, causing the halo effect that we see.
Did you know that the halo appearance that you see is uniquely personal to you? No two ice crystals are the same, and the way they reflect light will look different to you compared to someone standing next to you.
Taking a look at Connie's photo again, notice there isn’t much color with the halo itself. That’s because the light reflected off the moon isn’t nearly as bright when compared to sunshine. That’s why sun halos will have a brighter display of reds and blues.
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