A number of our viewers last night sent us pictures noting there was some odd halo around the moon. So the question is what caused this? I have to say Atmospheric Optics is something I find very interesting and wrote my senior thesis on this very subject in college! So how do these halos occur? Sometimes different particles in the atmosphere can create very cool visual displays like rainbows. I want to share a little info on what causes the halos and when you should look for them!
Here is the picture courtesy of the halo from last night taken by Nina Dotta...
Another awesome picture of the moon halo last night came to us courtesy of Debra Woods...
Most of us think of ice crystals in the atmosphere as snow flakes, but you may not have known that they are more often hexagonal columns. Here is an example donalbein of what happens to the moon or sunlight as it passes through one of these ice crystals. Notice the light is bent and spread into the colors you see.
Image courtesy of donalbein via wiki.
The hexagonal columns are the mechanism that creates the 22 degree halo you saw last night. When the sun or moon light shines through these columns, the light is bent and dispersed. As the light emerges from the crystal, it is bent normally 22 degrees creating the 22 degree halo normally seen. Here is an example of the process as the light moves through these ice crystals from the University of Illinois website.
The light is bent as it moves through the ice creating the atmospheric optical display known as halos! If you want to see one, just look toward the moon or sun (use caution to protect your eyes from the sun) when we have high cirrus clouds and you should see a halo! They are pretty common and some suggest we have near 100 per year in most locations.
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