Sunday, 24 November 2019

astronomy - How to explain the Moon halo phenomenon?


Today, here in Brazil, I have observed (and is still observing) an interesting phenomenon.


The Moon is near to a big star in the sky, but this is normal. The interesting part is what's around them.



A huge circle in which the moon and the star is inside. Why does this circle appear? What is it?


(This isn't a cloud. It looks like more something like a light reflection of a lamp.)


Unfortunately, I hadn't a good camera to catch this. I would appreciate having an image posted for this.



Answer



You might be describing a moon aura.


Moon Aura


It's caused by diffraction on tiny ice crystals in the atmosphere: When the moonlight hits the ice, you get interference effects that depend on the angle of the incident light. The idea is similar to powder diffraction in crystallography.


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