The Iridium flare
is a extremely bright (up to -8 magnitude
) streak of light across the sky
. For comparison, Venus
can be as bright as -4.9 (30x less bright). The flare can last anywhere from 5 to 20 seconds
before the satellite becomes invisible to the naked eye. Flares can also be observed during the daylight hours.
The Iridium flare is caused from sunlight reflecting off the antennae composed of highly reflective aluminum which are angled 40 degrees away from the axis of body which is perpendicular to the surface of the earth. The satellites themselves are rather small, about 4 meters long and less than one meter wide.
The precision of these satellites allows the occurrence of a flare to be accurately predicted. Charts for flare perdictions can be found at http://www.heavens-above.com/