Astronomical naming conventions sky have been named from ancient times. The scientific names are taken from the names given by the Romans: Mercury, Venus, Mars, Jupiter, and Saturn. Our own planet is usually named in English as Earth, or the equivalent in the language being spoken (for instance, two astronomers speaking French would call it "la Terre"). However, it is only recently in human history that it has been thought of as a planet. Earth, when viewed as a planet, is sometimes also called by its Latin scientific conventional name "Terra", this name is especially prevalent in science fiction where the adjective terran
Solar System icy objects. Astronomers sometimes informally divide this structure into separate regions. The inner Solar System includes the four terrestrial planets and the asteroid belt. The outer Solar System is beyond the asteroids, including the four giant planets. Since the discovery of the Kuiper belt, the outermost parts of the Solar System are considered a distinct region consisting of the objects beyond Neptune. Most of the planets in the Solar System have secondary systems of their own, being orbited by planetary objects called natural satellites, or moons (two of which, Titan and Ganymede, are larger than the planet Mercury), and, in