Exploration of Uranus
|
System
Spacecraft |
Jupiter | Saturn | Uranus | Neptune | Pluto |
|---|---|---|---|---|---|
| Pioneer 10 | 1973 flyby | ||||
| Pioneer 11 | 1974 flyby | 1979 flyby | |||
| Voyager 1 | 1979 flyby | 1980 flyby | |||
| Voyager 2 | 1979 flyby | 1981 flyby | 1986 flyby | 1989 flyby | |
| Galileo |
1995–2003 orbiter; 1995, 2003 atmospheric |
||||
| Ulysses | 1992, 2004 gravity assist | ||||
| Cassini–Huygens | 2000 gravity assist |
2004– orbiter; 2005 Titan lander |
|||
| New Horizons | 2007 gravity assist | 2015 flyby | |||
| Juno | 2016– orbiter |
The exploration of Uranus has, to date, been solely through telescopes and NASA's Voyager 2 spacecraft, which made its closest approach to Uranus on January 24, 1986. Voyager 2 discovered 10 moons, studied the planet's cold atmosphere, and examined its ring system, discovering two new rings. It also imaged Uranus' five large moons, revealing that their surfaces are covered with impact craters and canyons.
A number of dedicated exploratory missions to Uranus have been proposed, but as of 2016[update] none have been approved.
Voyager 2 made its closest approach to Uranus on January 24, 1986, coming within 81,500 kilometers (50,600 mi) of the planet's cloud tops. This was the probe's first solo planetary flyby, since Voyager 1 ended its tour of the outer planets at Saturn's moon Titan.
Uranus is the third-largest planet in the Solar System. It orbits the Sun at a distance of about 2.8 billion kilometers (1.7 billion miles) and completes one orbit every 84 years. The length of a day on Uranus as measured by Voyager 2 is 17 hours and 14 minutes. Uranus is distinguished by the fact that it is tipped on its side. Its unusual position is thought to be the result of a collision with a planet-sized body early in the Solar System's history. Given its odd orientation, with its polar regions exposed to sunlight or darkness for long periods, scientists were not sure what to expect at Uranus.
The presence of a magnetic field at Uranus was not known until Voyager's arrival. The intensity of the field is roughly comparable to that of Earth's, though it varies much more from point to point because of its large offset from the center of Uranus. The peculiar orientation of the magnetic field suggests that the field is generated at an intermediate depth in the interior where the pressure is high enough for water to become electrically conductive. Voyager 2 found that one of the most striking influences of the sideways position of the planet is its effect on the tail of the magnetic field, which is itself tilted 60 degrees from the planet's axis of rotation. The magnetotail was shown to be twisted by the planet's rotation into a long corkscrew shape behind the planet.
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