quasar175Calar Alto participates in a multi-observatory effort to study the most luminous quasar ever observed. The object, radio quasar 3C 454.3 in the constellation Pegasus, experienced during 2005 a strong optical outburst  that made it observable even with amateur instrumentation (reaching R = 12 mag). According to the WEBT team, "this ourburst peak likely represents the most luminous quasar state ever observed". The same team quantified the maximum luminosity of this object as MB = -31.4 mag. This means that, at its maximum and when observed in blue light, 3C 454.3 was as bright as 550 billions of suns put together...