Galilean moons

These five spots are planet Jupiter and its four biggest moons. On this picture, Jupiter is the brightest, surrounded by Io, Europa, Ganymede and Callisto, from the closest to the farthest (on the right of the image). They are called galilean moons after Galileo Galilei, the italian physicist and astronomer who observed them in 1610. His discovery of planets orbiting an object that wasn't Earth helped the paradigm shift from the ptolemaic world system. This picture was taken on October 22nd 2010 with a Nikon 3100 fitted with a 300 mm telelens and a doubler, aperture at f5.6, shutter at 1/8 sec and ISO at 3200.