Satellite flare
As an Iridium flare ( to German Iridium flickering) is a bright luminous phenomenon in the sky called, caused by reflection of sunlight on an Iridium satellite and about 5 to 20 seconds remaining. It is the brightest luminous phenomenon that cause artificial celestial bodies in the night sky; even on the day it is possible to observe Iridium flares.
Formation
The satellites make up the global Iridium satellite communications system with 66 telecommunications satellite in orbit. Each of these satellites has three Main Mission Antennae ( MMA), which have a size of 188 cm length, 86 cm wide and 4 cm thick. Its surface consists of highly reflective aluminum that is coated with a silver-colored Teflon layer, and acts as a plane mirror. Sunlight reflected from these antennas forms a narrow beam of light that sweeps in the appropriate orientation of the antenna on the ground surface. On his way to earth it widens to a diameter of several kilometers and may be perceived as a luminous appearance. Depending on the location of the observer, it may be a faint glow that is just to see with the naked eye, to a luminous appearance, which is similar to a flare. An Iridium flare, an apparent brightness up to -9 may achieve and shines about 50 times as bright as Venus and 1000 times as bright as Sirius, the brightest star in the night sky in this case.
Observation
The points in time at which a particular position can be seen from Earth Iridium flares, can be calculated down to the second. Corresponding orbital data and visibility predictions can be accessed online for any location on Earth, see Related links. The maximum brightness is seen only on a narrow band of around two kilometers wide, parallel to the satellite orbit. As the satellite orbits lead over the poles, these bands extend in a north-south direction. The further away you are from such a tape, the fainter the satellite appears. At 20 kilometers distance from the luminous phenomenon is not spectacular in the rule. Therefore, the location should be as well known.
On average, you can more than three Iridium flares per night see the lyre are brighter than the star Vega in the constellation. Approximately once a week, occurred an iridium flare, which is so bright that it is visible even in the day sky. The luminous phenomenon in this case is, however, significantly less spectacular than at night.
An Iridium flare is perceived as a wandering light spot whose brightness increases within a few seconds up to a maximum and then drops again. Owing to the motion of the satellites of this brightness curve is on photos with long exposure shown as a typical track ( see photos).