ABOARD CCGS AMUNDSEN—After a run of bad luck, the Amundsen experienced an omen last night, and it’s turning out to have been a good one.
For almost an hour, everyone could see three suns setting off the ship’s port side. The phenomenon is called “the sun’s dogs” — or sundogs — and is visible in southern Canada under rare atmospheric conditions.
In the supercold Arctic air, conditions are much more favourable, since what’s needed is a sun low on the horizon (check), an atmosphere heavy with ice crystals (check) and an absence of smog (double check).
Acting like miniature prisms, the ice crystals bend the sun’s rays at least 22 degrees so your eye sees two mock suns, one on each side of the real thing. As the photograph here shows, the dogs are squished vertically and also have a tail stretching away from the sun.
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| PETER CALAMAI PHOTO |
| Ice crystals in the frigid Arctic air combine with a sun low in the sky to create an atmospheric phenomenon known as sun dogs. |
An everyday rainbow is a reminder that sunlight is composed of a spectrum of colours, from red to blue. The colours have different wavelengths so they are bent or refracted different amounts by water droplets, spreading the sunlight out into a spectrum.
Something similar happens with sundogs, for which the scientific name is parhelia. If you look closely at the photograph, you’ll see the sundogs are reddish on the inner side, shading to blue on the outer.
There’s all sorts of neat physics involved in how the hexagonal ice prisms so often become aligned horizontally as they fall through the air, the position that produces the most spectacular sundogs.
Perhaps more interesting to us, however, is that yesterday the ship was finally settled in a secure berth and today a controlled frenzy of measurements, observations and experiments is underway. Maybe the sundogs smiled on us.
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