solar system
Since the early 1990s, astronomers have discovered other solar systems. A solar system has one or more planets orbiting one or more stars. We call these planets extrasolar planets, or exoplanets . They are called exoplanets because they orbit a star other than the Sun. As of April 2014, more than 4,600 exoplanets have been found, with 1706 confirmed. The rate of discovery is increasing rapidly! You can check out how many we have found at http://planetquest. jpl. nasa. gov/ .