A comet is an object following an oblong orbit around a star, and mainly compouned from dust and ice. When this celestial object gets closer to the sun, the irradation of the surface creates the evaporation of the ''dusty ice'' and the sun wind blows the vapor and creates the queue of the comet. It seems that the comets are originally from the Oort ring located at the ends of the Solar system. One of the most famous is Halley''s comet, whom the orbit has been calculated per the Astronom of the same name, but the most famous is the one which has been followed per the Three Wise Men. The first space machine which has studied teh queue of a comet was Pioneer 6, in 1973 (Kohoutek''s comet). Since, missions has succeded, in 1985 (Giacobini-Zinner''s comet), in 1986 (Halley''s comet, first pictures of the core of a comet), in 2002 (81P/Wild 2''s comet, first taking of dusts. During the return of the space probe Stardust in 2004, however, the space probe has not been able to be n''a pas pu être recuperated and it has crashed on the ground. The parts of the probe are still under analysis to find some dusts of the comet).