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| orbit_ref = 〔 | epoch = J2000 | aphelion = () | perihelion = () | semimajor = () | eccentricity = | period = | synodic_period = 369.66 days〔 | avg_speed = 6.80 km/s〔 | inclination = to ecliptic 6.48° to Sun's equator 1.02° to invariable plane〔 | asc_node = | arg_peri = | mean_anomaly = | satellites = 27 | physical_characteristics = yes | flattening = | equatorial_radius = 4.007 Earths〔 | polar_radius = 3.929 Earths〔 | mean_radius = 〔 | circumference = 〔 | surface_area = 〔 15.91 Earths | volume = 〔 63.086 Earths | mass = 14.536 Earths〔 GM= | density = 〔 | surface_grav = 〔 0.886 g | escape_velocity = 21.3 km/s〔 | sidereal_day = 〔 | rot_velocity = 2.59 km/s 9,320 km/h | axial_tilt = 97.77° (to orbit)〔 | right_asc_north_pole = 257.311°〔 | declination = −15.175°〔 | albedo = 0.300 (Bond) 0.51 (geom.)〔 | magnitude = 5.9〔 to 5.32〔 | angular_size = 3.3″ to 4.1″〔 | temperatures = yes | temp_name1 = 1 bar level〔 | min_temp_1 = | mean_temp_1 = | max_temp_1 = | temp_name2 = 0.1 bar (tropopause)〔 | min_temp_2 = 47 K | mean_temp_2 = 53 K | max_temp_2 = 57 K | pronounced = or 〔〔 | adjectives = Uranian | atmosphere = yes | atmosphere_ref = 〔〔〔 | scale_height = 27.7 km〔 | atmosphere_composition = ''(Below 1.3 bar)'' Gases: * 83 ± 3% hydrogen (H2) * 15 ± 3% helium (He) * 2.3% methane (CH4) * 0.009% (0.007–0.015%) hydrogen deuteride (HD) Ices: * ammonia * water * ammonium hydrosulfide * methane hydrate }} Uranus is the seventh planet from the Sun. It has the third-largest planetary radius and fourth-largest planetary mass in the Solar System. Uranus is similar in composition to Neptune, and both have different bulk chemical composition from that of the larger gas giants Jupiter and Saturn. For this reason, scientists often classify Uranus and Neptune as "ice giants" to distinguish them from the gas giants. Uranus's atmosphere, although similar to Jupiter's and Saturn's in its primary composition of hydrogen and helium, contains more "ices", such as water, ammonia, and methane, along with traces of other hydrocarbons.〔 It is the coldest planetary atmosphere in the Solar System, with a minimum temperature of , and has a complex, layered cloud structure, with water thought to make up the lowest clouds, and methane the uppermost layer of clouds.〔 The interior of Uranus is mainly composed of ices and rock.〔 Uranus is the only planet whose name is derived from a figure from Greek mythology, from the Latinized version of the Greek god of the sky, Ouranos. Like the other giant planets, Uranus has a ring system, a magnetosphere, and numerous moons. The Uranian system has a unique configuration among those of the planets because its axis of rotation is tilted sideways, nearly into the plane of its revolution about the Sun. Its north and south poles therefore lie where most other planets have their equators.〔 In 1986, images from ''Voyager 2'' showed Uranus as an almost featureless planet in visible light, without the cloud bands or storms associated with the other giant planets.〔 Observations from Earth have shown seasonal change and increased weather activity as Uranus approached its equinox in 2007. Wind speeds can reach 250 metres per second (900 km/h, 560 mph).〔 == History == Though Uranus is visible to the naked eye like the five classical planets, it was never recognized as a planet by ancient observers because of its dimness and slow orbit.〔(【引用サイトリンク】work=Monterey Institute for Research in Astronomy )〕 Sir William Herschel announced its discovery on March 13, 1781, expanding the known boundaries of the Solar System for the first time in history. Uranus was the first planet discovered with a telescope. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Uranus」の詳細全文を読む スポンサード リンク
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