Astronomy Picture of the Day . ... 7.01.2006 . ... The region's spidery appearance is responsible for its popular name, the Tarantula Nebula, except that this tarantula is about 1,000 light-years across, and 180,000 light-years away in the southern constellation Dorado. ... Iapetus, the third largest moon of Saturn, was inspected again as the Saturn-orbiting robot Cassini spacecraft swooped past the enigmatic world again late last year. ... APOD: 2006 January 1- The Largest Rock in the Solar System . ...