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Observations From Earth, Results From The Flyby Of The Voyager 2 Spacecraft, Uranus's Magnetic FieldDiscovery, Puck

Uranus is the seventh planet from the Sun. It has a large size (its diameter is almost four times that of Earth) and mass, low mean density, fairly rapid rotation, and well-developed ring (11 components) and satellite (15 members) systems. The planet has a strong magnetic field with a large tilt (58.6°) to its rotation axis and offset (0.3 Uranus radius) from its center. Analysis of the observations made by Voyager 2 during its flyby of Neptune in August 1989 shows that Uranus and Neptune are similar in most of these properties and form a subgroup of the Jovian planets; Jupiter and Saturn, much larger and more massive, form the other subgroup.

William Herschel (1738–1822) fortuitously discovered Uranus in 1781; it was the first planet discovered telescopically. It was found to orbit the sun at a mean distance of about 19.2 astronomical units (a.u.) (2,870,000,000 km), about twice as far from the sun as Saturn (9.54 a.u), the most distant planet known before 1781.

Puck's surface was also imaged by Voyager 2, revealing a cratered surface that is considerably darker (0.08 average albedo) than that for any of the five larger satellites. The Voyager 2 images also show that Puck is almost spherical. The three largest impact craters on Puck are named Bogle, Lob, and Butz.



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Arnett, B. SEDS, University of Arizona. "The Nine Planets, a Multimedia Tour of the Solar System." (November 6, 2002) [cited February 8, 2003]. <http://seds.lpl.arizona.edu/nineplanets/nineplanets/nineplanets.html>.

Frederick R. West

David T. King, Jr.

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Science EncyclopediaScience & Philosophy: Two-envelope paradox to Venus