A bright flash in the sky

There are hundreds of operational satellites and thousands of unused satellites and satellite fragments orbiting the Earth. A few of these are quite bright and easy to see as they traverse the sky. Most are dim and generally not easily visible. And others are usually dim but briefly flare much brighter.

Satellite flare is caused by the reflective surfaces on satellites reflecting sunlight directly onto the Earth below and appearing as a brief, bright “flare.” The Iridium satellite series is especially conducive to reflecting light back to the earth and these flares can be exceptionally bright.

Satellite flare from Iridium 91 as it traverses the northern Arizona sky.
Satellite flare from Iridium 91 as it traverses the northern Arizona sky.

Here is an example of the Iridium 91 satellite as it traversed the northern Arizona sky and quickly brightened to a magnitude of -7.0 . Only the Moon (-13) and the Sun (-27) have brighter magnitudes.

Detail of a satellite flair from Iridium 91 as it traverses the northern Arizona sky.
Detail of a satellite flair from Iridium 91 as it traverses the northern Arizona sky.

Knowing when and where to look for Iridium flares is easy as there are many web sites that provide this information. My favorites are Heavens-Above.com and CalSky.com. Happy satellite viewing!