EarthSky Facebook friend Ken Christison in North Carolina caught this halo around the moon earlier this week (October 21, 2013). And in fact we’ve seen many photos of lunar halos in the past week, on EarthSky’s Facebook page.
These halos – sometimes called winter halos – do seem to appear more often in winter. They result from high thin cirrus clouds drifting 20,000 feet or more above our heads.
These clouds contain millions of tiny ice crystals. The halos you see are caused by both refraction, or splitting of light, and also by reflection, or glints of light from these ice crystals. The crystals have to be oriented and positioned just so with respect to your eye, in order for the halo to appear.
These sorts of clouds also come before a storm, so there’s truth to the old saying: halo around the moon means rain soon.
Thank you, Ken!