August 29, 2010
Photographer: Jane Shively
Summary Author: Jane Shively; Jim Foster
The photo above looks like it could have been taken from a planet in a solar system having twin suns; though, it was snapped from a back yard in northern Ohio. Can you tell which is the real Sun and which is a fraud? Hint: Our constant companion is a little less showy. The true Sun is at left, and at right is a sundog. Sundogs or parhelia can be amazingly bright at times. They're found on either side of the Sun, at the same altitude, but 22 degrees away from it. Sundogs form when sunlight is refracted through oriented, hexagonal (plate-shaped) ice crystals in cirrus clouds. Sunlight enters one of the crystal's side faces and exits through an alternate side face -- refracted 22 degrees from the angle it entered. When the Sun is low is the sky, sundogs are at their brightest. On this day, it's likely that a combination of the Sun being dimmed by cloud cover and ice crystals having almost the same orientation, accounted for the near similar brightness of the Sun and its mocking sidekick.
Photo details: Camera Maker: SONY; Camera Model: CYBERSHOT; Focal Length: 6.1mm; Aperture: f/8.0; Exposure Time: 0.0021 s (1/475); ISO equiv: 100; Exposure Bias: none; Metering Mode: Center Weight; Exposure: program (Auto); Flash Fired: No; Color Space: sRGB.