<P> He named it Saturni Luna (or Luna Saturni, Latin for "Saturn's moon"), publishing in the 1655 tract De Saturni Luna Observatio Nova (A New Observation of Saturn's Moon). After Giovanni Domenico Cassini published his discoveries of four more moons of Saturn between 1673 and 1686, astronomers fell into the habit of referring to these and Titan as Saturn I through V (with Titan then in fourth position). Other early epithets for Titan include "Saturn's ordinary satellite". Titan is officially numbered Saturn VI because after the 1789 discoveries the numbering scheme was frozen to avoid causing any more confusion (Titan having borne the numbers II and IV as well as VI). Numerous small moons have been discovered closer to Saturn since then . </P> <P> The name Titan, and the names of all seven satellites of Saturn then known, came from John Herschel (son of William Herschel, discoverer of Mimas and Enceladus) in his 1847 publication Results of Astronomical Observations Made during the Years 1834, 5, 6, 7, 8, at the Cape of Good Hope . He suggested the names of the mythological Titans (Ancient Greek: Τῑτάν), brothers and sisters of Cronus, the Greek Saturn . In Greek mythology, the Titans were a race of powerful deities, descendants of Gaia and Uranus, that ruled during the legendary Golden Age . </P> <P> Titan orbits Saturn once every 15 days and 22 hours . Like the Moon and many of the satellites of the giant planets, its rotational period (its day) is identical to its orbital period; Titan is tidally locked in synchronous rotation with Saturn, and permanently shows one face to the planet, so Titan's "day" is equal to its orbit period . Because of this, there is a sub-Saturnian point on its surface, from which the planet would always appear to hang directly overhead . Longitudes on Titan are measured westward, starting from the meridian passing through this point . Its orbital eccentricity is 0.0288, and the orbital plane is inclined 0.348 degrees relative to the Saturnian equator . Viewed from Earth, Titan reaches an angular distance of about 20 Saturn radii (just over 1,200,000 kilometers (750,000 mi)) from Saturn and subtends a disk 0.8 arcseconds in diameter . </P> <P> The small, irregularly shaped satellite Hyperion is locked in a 3: 4 orbital resonance with Titan . A "slow and smooth" evolution of the resonance--in which Hyperion migrated from a chaotic orbit--is considered unlikely, based on models . Hyperion probably formed in a stable orbital island, whereas the massive Titan absorbed or ejected bodies that made close approaches . </P>

How long does it take for titan to orbit saturn