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Relax. That very bright light in the skies of northeastern Salt Lake City Monday night was not an invasion fleet from Alpha Centauri, bent on enslaving humankind.
But there's no doubt that it was spectacularly bright, says Clark Planetarium Director Seth Jarvis.
"Yep, an Iridium flare. Brilliant. About 10 times brighter than Venus," Jarvis confirmed Tuesday. "There was also an extremely bright Iridium flare Sunday night, and a nice pass straight overhead of the International Space Station, all within a span of 20 minutes."
Another flare was expected Tuesday night, specifically at 9:00:48 p.m. Look north, about 30 degrees above the horizon. "The flare will start slowly, probably about 10 seconds before peak," Jarvis says.
The flare is caused by a namesake "Iridium" communications satellite as it reflects sunlight. There currently are 66 such satellites orbiting the planet; each has large, mirror-like antennas that "reflect sunlight in very narrow, but exceptionally bright, paths across the surface of the Earth," he says.
The light show of the past night or two can occur when the satellite is still in sunlight at the same time a ground location is still in the dark, but nonetheless in the path of reflected light from Old Sol. The resulting flare is both dramatic, and short-lived, lasting only a few seconds.
Good news for sky-watchers: Iridium flares are highly predictable.
Jarvis suggests checking the website http://www.heavens-above.com to learn when future flares will appear in the local night sky.
"You just create an account and enter your location information and then the web page calculates visibility schedules for the International Space Station, Iridium flares, and several other satellite observation opportunities," he said.