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
GREGOR Solar Telescope GREGOR Solar Telescope GREGOR is a solar telescope, equipped with a 1.5 m primary mirror. located at the Teide Observatory on Tenerife in the Canary Islands. It replaces the older Gregory Coudé Telescope and was inaugurated on May 21, 2012. First light was on . GREGOR is the third-largest solar telescope in the world, after the Big Bear Observatory and the McMath-Pierce solar telescope. It is aimed at observing the solar photosphere and chromosphere at visible and infrared wavelengths. GREGOR sports a high-order adaptive optics (AO) system with a 256-actuator deformable mirrors and a 156-subaperture Shack-Hartmann wavefront sensor. Efforts are