Uranus
seventh planet in the Solar System from the Sun / From Wikipedia, the free encyclopedia
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Discovery | |||||||||||||
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Discovered by | William Herschel | ||||||||||||
Discovery date | 13 March 1781 | ||||||||||||
Designations | |||||||||||||
Pronunciation | /jʊˈreɪnəs/ (listen)[1][2] or /ˈjʊərənəs/ (listen) | ||||||||||||
Named after | the Latin form Ūranus of the Greek god Οὐρανός Ouranos | ||||||||||||
Adjectives | Uranian (/jʊˈreɪniən/)[3] | ||||||||||||
Orbital characteristics[4][lower-alpha 1] | |||||||||||||
Epoch J2000 | |||||||||||||
Aphelion | 20.0965 AU (3006.39 Gm) | ||||||||||||
Perihelion | 18.2861 AU (2735.56 Gm) | ||||||||||||
19.19126 AU (2870.972 Gm) | |||||||||||||
Eccentricity | 0.04717 | ||||||||||||
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369.66 days[7] | |||||||||||||
Average orbital speed | 6.80 km/s[7] | ||||||||||||
142.238600° | |||||||||||||
Inclination |
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74.006° | |||||||||||||
17–19 August 2050[9][10] | |||||||||||||
96.998857° | |||||||||||||
Known satellites | 27 | ||||||||||||
Physical characteristics | |||||||||||||
Mean radius | 25,362±7 km[11][lower-alpha 2] | ||||||||||||
Equatorial radius | 25,559±4 km 4.007 Earths[11][lower-alpha 2] | ||||||||||||
Polar radius | 24,973±20 km 3.929 Earths[11][lower-alpha 2] | ||||||||||||
Flattening | 0.0229±0.0008[lower-alpha 3] | ||||||||||||
Circumference | 159,354.1 km[5] | ||||||||||||
8.1156×109 km2[5][lower-alpha 2] 15.91 Earths | |||||||||||||
Volume | 6.833×1013 km3[7][lower-alpha 2] 63.086 Earths | ||||||||||||
Mass | (8.6810±0.0013)×1025 kg 14.536 Earths[12] GM=5,793,939±13 km3/s2 | ||||||||||||
Mean density | 1.27 g/cm3[7][lower-alpha 4] | ||||||||||||
8.69 m/s2[7][lower-alpha 2] 0.886 g | |||||||||||||
0.23[13] (estimate) | |||||||||||||
21.3 km/s[7][lower-alpha 2] | |||||||||||||
−0.71832 d −17 h 14 m 23 s (retrograde)[6] | |||||||||||||
Sidereal rotation period | −0.71833 d −17 h 14 min 24 s (retrograde)[11] | ||||||||||||
Equatorial rotation velocity | 2.59 km/s 9,320 km/h | ||||||||||||
97.77° (to orbit)[7] | |||||||||||||
North pole right ascension | 17h 9m 15s 257.311°[11] | ||||||||||||
North pole declination | −15.175°[11] | ||||||||||||
Albedo | 0.300 (Bond)[14] 0.488 (geom.)[15] | ||||||||||||
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5.38[18] to 6.03[18] | |||||||||||||
3.3″ to 4.1″[7] | |||||||||||||
Atmosphere[17][19][20][lower-alpha 5] | |||||||||||||
27.7 km[7] | |||||||||||||
Composition by volume | (Below 1.3 bar) Gases:
Ices:
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Uranus is the seventh planet from the Sun in our Solar System. Like Neptune, it is an ice giant. It is the third largest planet in the solar system.
The planet is made of ice, gases and liquid metal. Its atmosphere contains hydrogen (1H), helium (2He) and methane. The temperature on Uranus is −197 °C (−322.6 °F; 76.1 K) near the top of its atmosphere. Its small solid core (about 55% the mass of Earth) is probably about 4,730 °C (8,540 °F; 5,000 K).
The planet is tilted on its axis so much that it is sideways.[22] The cause of this is not known for certain. It has five big moons, many small ones, and a small system of 13 planetary rings.
The distance between Uranus and the Sun is about 2.8 billion km. Uranus completes its orbit around the Sun in 84 earth years. It completes a spin around its axis in 17 hours and 14 minutes. This means there are about 43,000 Uranian days in one Uranian year.[23]
Uranus was discovered in 1781.[24] This planet can be seen with the naked eye under perfect conditions. John Flamsteed saw it decades earlier but mistook it for a star (34 Tauri).
Near the solstice, one pole faces the Sun continuously and the other faces away. Only a narrow strip around the equator has a rapid day–night cycle, with the Sun low over the horizon. Each pole gets around 42 years of continuous sunlight, followed by 42 years of darkness.
Uranus is named after Uranus, the Greek name of the Sumerian god Anu,[25] who was a god of the sky.