We have now reached the poorly-explored realm of the ice giants and so-called Trans-Neptunian Objects. In the past half-century the human race has sent only a handle of probes to this vast region.
Uranus was visible for centuries before its “discovery”, but was usually ignored as just some star. It was William Herschel who in 1781 finally resolved it as a blue disk (all stars appear as points), though he originally mistook it to be a comet. Uranus is fairly unique in that its axis of rotation lies in the plane of the solar system; it’s “knocked on its side”. Why this is is still the subject of investigation.
Modern Exploration of Uranus:
- Voyager 2 (1986) – NASA flyby mission, on a “grand tour” of the outer solar system. Virtually all of our knowledge on the Uranian system that can not be obtained from Earthbound telescopes is from the Voyager 2 mission. It investigated its atmosphere, imaged the planet and its major moons, and discovered new rings and moons. Here is Voyager 2’s final shot of the planet.
- Various other missions to Uranus have been proposed, but it’s arguably too early to make any reasonable projections.