A ring around the Sun seen by people around the northeast on Monday and Tuesday was the result of ice crystals high in the sky.
The effect, known as a sun halo, solar halo or 22-degree halo, gives our home star the look of being surrounded by a circle of light. Ice crystals which make up cirrostratus clouds high in the sky refract the light from the Sun, breaking it up into the colors of a rainbow. These particles of light spread out at an angle of 22 degrees in all directions, creating the halo effect. This is the same type of cloud that causes hazy sunshine.
The effect was caused by a warm front approaching the northeast, lifting moisture high into the air. This causes billions of ice crystals to act like floating prisms for any light streaming through them. Not every ice crystal can cause this effect - they must be long and thin, having six sides, to provide the proper bend to the light in order to create a solar halo.
Walter Drag of the National weather Service said such halos are "a very folklorist predictor of rain. It doesn't always work out that way, however."
Although this phenomenon was sighted this time circling the sun, the same effect can occur at night, around the Moon. Although this is a fairly common occurrence, the show seen in the skies over the northeast on Monday and Tuesday was a rare example of solar halos at their most dramatic.
Patrick O'Hara of the National Weather Service said "It's not that uncommon, but it's not something you see every day."
Sun halos are often confused with Sun dogs, which are created by a similar process. Sun dogs, however, produce one or two "false Suns" which sit to either side of the real star, rather than taking on a ring formation.
People on the Jersey Shore who had come out to see Prince Harry and Governor Chris Christie got a perfect view of the atmospheric phenomenon on Tuesday. Some skywatchers reported seeing the effect from as far west as the lower Great Lakes, and as far south as Baltimore.