Blog #2 Lunar Corona (aka aliens?)

Saturday January 19th on my nightly stroll back to my dorm with crappy lighting my friend looked up at the sky and asked if the world was ending. I proceeded to stop and what I saw made me stop dead in my tracks. It was gorgeous, there was a beautiful, perfect looking ring around the moon. Of course I took a picture and started planning this blog post, what is better lighting to write about that crazy natural lighting phenomenon? I've included my crummy picture and to match I will write about my equally crummy research on why this ring happened.

Firstly I would like to say I am entirely unqualified to actually talk about the science of this but I find it interesting so I will share what I tentatively and perhaps incorrectly have learned. According to Wikipedia and a science blog this ring was one of two things, it is a lunar corona or it could be a 22 degree halo. A lunar corona is any circle like this around the moon and it doesn't have to be as complete as this one was. Basically this kind of ring is produced when moonlight (and less commonly sunlight and even more rarely really bright starlight) is diffracted by water droplets or ice crystals in the atmosphere. The water droplets/ice crystals act like a lens and cause the light to bend creating a halo around the moon. The size of the corona depends on the size of the particles diffracting the light, so smaller particles cause larger coronae. Coronae often have a hazier ring and can have several colored-ish rings making up the halo.

The other option as to what this mysterious lunar ring could be is a 22 degree halo. The difference between coronae and the 22 degree halo is that the halo is caused by refraction off of specifically ice crystals rather than the coronae being caused by diffraction off of normally water droplets. Honestly I don't really know what this means but that is the distinction. The halo also has the distinction of being roughly 22 degrees in radius around the moon, hence the name. Based on my own observations the halo seems much more clear and defined than the coronae which makes me think what I saw was the halo because it was so clear and not really fuzzy at all like it seems most coronae are. I suppose I could get my protractor out and check but I figure it doesn't matter quite that much.

Regardless of what the ring was it was beautiful and I am very glad that I got to see it. Then I got to see an lunar eclipse the next night but that's a whole different thing. Overall it was a great couple days for lunar events.