Zeta UMa Observatory


La constelación de satellites Iridium se caracteriza por la forma peculiar de sus 66 componentes: cada satélite posee 3 antenas brillantes separadas 120 grados, que reflejan muy bien la luz del sol. Ocasionalmente, una de las antenas la proyecta directamente sobre la superficie terrestre, creando un destello de luz móvil en el cielo, predecible, y de unos pocos segundos de duración, que puede incluso alcanzar la magnitud -9.5 y ser visible durante el día. 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 reflect sunlight directly 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 few seconds. Ranging up to -8 magnitude (rarely to a brilliant -9.5), some of the flares are so bright that they can be seen at daytime; but they are most impressive at night. This flashing has been some annoyance to astronomers, as the flares occasionally disturb observations and can damage sensitive equipment. When not flaring, the satellites are often visible crossing the night sky at a typical magnitude of 6, similar to a dim star.
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