It's a halo!

Photo by Peggy Wenrick 4/10/2012

On the plant walk yesterday, we saw (among many other things) this ring around the sun. One was spotted in Sydney Australia last month. According to this weather service site, a complete ring is called a halo; if there are only two spots on either side, it's a sun dog:

In ages past, the huge rings or haloes around the sun or the moon were thought to portend everything from storms to great personal disasters. We now know that they are the optical result of the refraction of light from the sun or moon by ice crystals in the very high cloud (25,000 feet or higher) called cirrus or cirrostratus. On occasion, only two bright spots on either side of the sun can be seen. These are known as sun dogs and are caused when the ice crystals occur in a certain uniform arrangement.