They suspect there are two more, including one that could be the smallest found outside our solar system.
Christophe Lovis of Geneva University says the discovery was made by Swiss, French and German scientists using the European Southern Observatory telescope in Chile.
Lovis said Tuesday that the planets orbit a star called HD 10180 some 127 light-years away in the Hydrus constellation.
Five are covered with rock and ice, and have 13 to 25 times the mass of Earth.
Scientists also suspect the system contains one larger planet similar to Saturn and another with only 1.4 times the mass of Earth orbiting very close to the star.