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The timeline of discovery of Solar System planets and their natural satellites charts the progress of the discovery of new bodies over history. Each object is listed in chronological order of its discovery (multiple dates occur when the moments of imaging, observation, and publication differ), identified through its various designations (including temporary and permanent schemes), and the ...
These are lists of planets.A planet is a large, rounded astronomical body that is neither a star nor its remnant. The best available theory of planet formation is the nebular hypothesis, which posits that an interstellar cloud collapses out of a nebula to create a young protostar orbited by a protoplanetary disk.
All planets in the Solar System, plus their major moons along some asteroids and comets, have now been visited to varying degrees by spacecraft launched from Earth. Through these uncrewed missions, humans have been able to get close-up photographs of all the planets and, in the case of landers, perform tests of the soils and atmospheres of some.
Mission name Launch date Description Ref(s) Sputnik 1: 4 October 1957 First Earth orbiter [1] [2] Sputnik 2: 3 November 1957 Earth orbiter, first animal in orbit, a dog named Laika [2] [3] [4] Explorer 1: 1 February 1958 Earth orbiter; discovered Van Allen radiation belts [5] Vanguard 1: 17 March 1958 Earth orbiter; oldest spacecraft still in ...
In antiquity, it was believed that the Sun and all the planets orbit the Earth. Thus the Sun was categorised as a planet. Following the acceptance of the Copernican model, it was recognized that the planets (including Earth) orbit the Sun, and it was no longer regarded as a planet. Subsequent discoveries show that the Sun is a star.
Seven Earth-sized planets have been discovered orbiting a nearby star, three of which appear to be warm enough to sustain life, according to astronomers from NASA and the European Southern ...
By RYAN GORMAN Scientists may have found Planet X -- the long-rumored object believed to be larger than Earth and further from the sun than Pluto. Planet X and another object dubbed "Planet Y ...
1979 – Pioneer 11 flies by Saturn, providing the first ever closeup images of the planet and its rings. It discovers the planet's F ring and determines that its moon Titan has a thick atmosphere. [199] 1979 – Goldreich and Tremaine postulate that Saturn's F ring is maintained by shepherd moons, a prediction that would be confirmed by ...