Discovery and exploration of the Solar System Domenico Cassini later discovered four more moons of Saturn and the Cassini division in Saturn's rings. Edmond Halley realised in 1705 that repeated sightings of a comet were recording the same object, returning regularly once every 75–76 years. This was the first evidence that anything other than the planets orbited the Sun. Around this time (1704), the term "Solar System" first appeared in English. In 1781, William Herschel was looking for binary stars in the constellation of Taurus when he observed what he thought was a new comet. Its orbit revealed that it was a new planet, Uranus, the first
Giant planet with Jupiter than with the other giant planets, some have claimed that "jovian planet" is a more accurate term for them. Many of the exoplanets are much closer to their parent stars and hence much hotter than the giant planets in the Solar System, making it possible that some of those planets are a type not observed in the Solar System. Considering the relative abundances of the elements in the universe (approximately 98% hydrogen and helium) it would be surprising to find a predominantly rocky planet more massive than Jupiter. On the other hand, models of planetary-system formation have suggested