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Uranus Brief History 7 th Planet from the Sun 3 rd largest planet by mass Named after the ancient Greek god for Heaven Discovered in 1781 by William Herschel Visited by Voyager 2 on January 24, 1986 Statistics Distance from Sun: 2.87 billions kilometers; 19.22 AU
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Brief History • 7th Planet from the Sun • 3rd largest planet by mass • Named after the ancient Greek god for Heaven • Discovered in 1781 by William Herschel • Visited by Voyager 2 on January 24, 1986
Statistics • Distance from Sun: 2.87 billions kilometers; 19.22 AU • Diameter: 51,118 km; 4.01 Earth Diameters • Mass: 8.683e25 kg; 14.535 Earth Mass • Satellites: 21 named moons and 6 unnamed moons • Composition: mostly rock and ice; only about 15% Hydrogen • Atmosphere: 83% Hydrogen • 15% Helium • 2% Methane
Statistics • Orbit around sun: 84.01 earth years • Day: 17 hours 14 minutes • Color: Blue-green color; due to Methane gas in the upper atmosphere which absorbs red light • Density: 1.2 g/cm3 • Albedo: 0.35
Internal Structure • Similar to Neptune’s • Outer envelop: hydrogen, helium and methane about the mass of 1-2 earths • Mantle: water, methane, and ammonia under high pressure and temperature, about 10-15 earth masses • Core: rock and ice, about 1 earth mass
Uranus’ Rings • First 9 rings discovered in 1977 • 11 known rings • Very dark and faint • Outermost rings is the brightest: Epsilon • Composed of fine dust to large particles of ice boulders up to 10 meters in diameter • Most rings 2-12 km across
Uranus Rings • Shepherd moons keep the dust in rings • Without the moons’ gravity the rings would spread apart until they disappeared
Uranus’ Moons • 21 named moons and 6 unnamed moons • Named after writings of Shakespeare and Pope • Mostly circular orbits except outermost four, which are much more elliptical • 3 distinct classes: 11 small, dark inner moons 5 large moons Newly discovered further out moons
Titania • Largest moon • Radius: 788 km • Mass: 3.49e21 kg • Distance from Uranus: 435,840 • Density: 1.7 gm/cm3
Oberon • 2nd largest moon • Radius: 761.4 km • Mass: 3.03e 21 kg • Distance from Uranus 582,600 km • Density: 1.64 gm/cm3
Moon Characteristics • Like our own moon • Most are covered in craters and trenches • A few mountains • Icy
Uranus is Weird • Uranus is tipped on its side • Result of a planetoid colliding with it • This causes the magnetic field to be tilted 60 degrees from the planet’s axis of rotation • The source of the magnetic field is unknown and the the tail was twisted into a corkscrew by the collision
Voyager 2 • Launched on April 20, 1977 • Passed Uranus on January 24, 1986