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
Stability of the Solar System becoming significantly more—or less—elliptical. In calculation, the unknowns include asteroids, the solar quadrupole moment, mass loss from the Sun through radiation and solar wind, drag of solar wind on planetary magnetospheres, galactic tidal forces, and effects from passing stars. Furthermore, the equations of motion describe a process that is inherently serial, so there is little to be gained from using massively parallel computers. The Neptune–Pluto system lies in a 3:2 orbital resonance. C.J. Cohen and E.C. Hubbard at the Naval Surface Warfare Center Dahlgren Division discovered this in 1965. Although the resonance itself will remain stable in the short term,