Iridium Flare

I just saw an Iridium flare this morning when I went out to pick up the newspaper. The first time I heard the guys at the astronomy club mention seeing Iridium flares, I had no idea what they were talking about. What phenomenon of nature was that? It turns out it is not a natural phenomenon, but a man-made one. The Iridium satellites are small communication satellites orbiting the Earth with antennas that can give off a spectacular flare when angled to the sun just right. (Whether you can call these bursts of bright light a glint, a flash, or a flare is explained here.) This one occurred at 6:23:29 am PDT as the sun was rising. So it was not exactly daylight, but the sky was very bright. Venus and Saturn were visible in the east and Sirius was holding forth in the south-southeast.

There is a web page, called Heavens Above, which has tons of information about astronomy and will predict for you when a flare is going to occur at your location. This flare (my judgement) was extremely bright—magnitude -6. It lasted for several seconds and moved upward and spread outward briefly, then vanished. The particular satellite was the Iridium 25 which was launched from Vandenburg AFB in 1997. Heavens Above will even tell you which antenna caused the flare. In this case it was the left antenna. Amazing!