Transcript: Jupiter and Saturn have been known for thousands of years. They've given their names to two of the days of our week. Uranus was discovered in 1781 by the astronomer William Hershel accidentally during a star mapping project. It was a moving target among the pattern of star fields that he was observing. Hershel could not make out any detail on the planet, but he was able to calculate its orbit from its motions measured over several years. Thus Hershel became the first known human to discover a planet. In Greek mythology Uranus is the father of Saturn who is the father of Jupiter. In the entire time since its discovery Uranus has completed less than three orbits of the Sun. Compare this to fleet-footed Mercury, the innermost planet, which completes several orbits of the Sun every year.