There's something strange about Sirius. The brightest star in the sky is pulsing with color. To the naked eye, Sirius looks pale blue, almost white. But if you photograph it with a camera, using very short exposure times, Sirius reveals its true colors. Lots of them. Photographer Arne Recke of Broager, Denmark, just did the experiment, and this is what he found:
"Here are 16 pictures of Sirius," says Recke. "The uppermost picture was taken with 1/2 sec. shutter speed (ISO 6400). The other 15 pictures were taken much faster with a 1/500 sec.shutter speed (also ISO 6400). The short exposures are incredibly colorful."
Astronomers call this phenomenon "scintillation." It is caused by thermal irregularities in Earth's atmosphere. Packets of relatively warm and cool air act like prisms, spreading starlight into rainbow colors. When these packets drift in front of Sirius--voilá.
The reason Recke's first exposure looks white is because 1/2 sec. is long enough to average many colors together. Multiple packets of air drift by during that time. The shorter snapshots, however, capture individual packets; they look like tiny supernova explosions.
All stars scintillate, but Sirius does so most flamboyantly because of its extreme brightness. See for yourself. Step outside this evening an hour or so after sunset and look east for Sirius near the feet of Orion. The lower it is, the more it scintillates. You may be able to see the colors--no camera required.
www.spaceweather.com
Astronomers call this phenomenon "scintillation." It is caused by thermal irregularities in Earth's atmosphere. Packets of relatively warm and cool air act like prisms, spreading starlight into rainbow colors. When these packets drift in front of Sirius--voilá.
The reason Recke's first exposure looks white is because 1/2 sec. is long enough to average many colors together. Multiple packets of air drift by during that time. The shorter snapshots, however, capture individual packets; they look like tiny supernova explosions.
All stars scintillate, but Sirius does so most flamboyantly because of its extreme brightness. See for yourself. Step outside this evening an hour or so after sunset and look east for Sirius near the feet of Orion. The lower it is, the more it scintillates. You may be able to see the colors--no camera required.
www.spaceweather.com
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