... Only 20,000 light-years away in the constellation Sagittarius, M55 appears to earth-bound observers to be nearly 2/3 the size of the full moon. ... Two years ago, images from the robotic Cassini spacecraft orbiting Saturn led astronomers to the undeniable.. ... Spiral Galaxy NGC 2841 . ... Launched from Earth in 1997, robotic Cassini entered orbit around Saturn in 2004 and has revolutionized much of humanity's knowledge of Saturn, its expansive and complex rings, and it many old and battered moons. ...