In all its glory

While on a plane trip, I saw a strange phenomenon:

See it? Let's make that a little clearer by adding contrast.

Cool, ain't it? First, I thought it was just a reflection of the window on the other side of the plane, but then I guess it wasn't, since there wasn't a window open. The faint apparition-like halo may have been just an illusion. Maybe I was gazing too much at the window. Maybe not...

After some brief searching, I found the best explanation for it: Glory. It's a "glory", a refractive effect caused by the sun shining onto the clouds.