Satellite flare

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A simulated animation of a typical iridium flare.

Iridium Flare and comet 17P/Holmes

A 30-second exposure of a flare produced by an Iridium satellite.

Iridium flare observed on November 26th, 2006 from Tübingen, Germany

Satellite flare (also known as satellite glint) is the phenomenon caused by the reflective surfaces on satellites (such as antennas or solar panels) reflecting sunlight directly onto the Earth below and appearing as a brief, bright "flare".

[edit] Iridium satellite flare

The Iridium communication satellites have a peculiar shape with three polished door-sized antennas, 120 degrees apart and at 40 degree angles with the main bus. The forward antenna faces the direction in which the satellite is travelling. Occasionally an antenna will directly reflect sunlight down to the Earth, creating a predictable and quickly moving illuminated spot of about 10 km diameter. To an observer this looks like an extremely bright flare in the sky with a duration of a couple of seconds or longer.

Some of the flares are so bright (some get up to -8 magnitude, but rarely they can get to a brilliant -9.5)^[1] that they can be seen at daytime, but they are most impressive at night. This flashing has been of extreme annoyance to astronomers^{[citation needed]}, as the flares occasionally disturb observations and can damage sensitive equipment.

When not "flaring," the satellites are often still just visible to the naked eye — a typical magnitude is 6, similar to a dim star.