7️⃣ Uranus

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 Jupiterand Saturn. For this reason, scientists often classify Uranus and Neptune as “ice giants” to distinguish them from the gas giants. Uranus’s atmosphere is similar to Jupiter’s and Saturn’s in its primary composition of hydrogen and helium, but it contains more “ices” such as water, ammonia, and methane, along with traces of other hydrocarbons.[12] It is the coldest planetary atmosphere in the Solar System, with a minimum temperature of 49 K (−224 °C; −371 °F), and has a complex, layered cloud structure with water thought to make up the lowest clouds and methane the uppermost layer of clouds.[12] The interior of Uranus is mainly composed of ices and rock.[11]

Uranus Uranus symbol.svg

Uranus as a featureless disc, photographed by Voyager 2 in 1986
Discovered by William Herschel
Discovery date March 13, 1781
Pronunciation /ˈjʊərənəs/ (About this sound listen)or /jʊəˈrnəs/ (About this sound listen)[1][2]
Adjectives Uranian
Orbital characteristics[7][a]
Epoch J2000
Aphelion 20.11 AU
(3,008 Gm)
Perihelion 18.33 AU
(2,742 Gm)
19.2184 AU
(2,875.04 Gm)
Eccentricity 0.046381
369.66 days[5]
6.80 km/s[5]
Inclination 0.773° to ecliptic
6.48° to Sun‘s equator
1.02° to invariable plane[6]
Known satellites 27
Physical characteristics
Mean radius
25,362±7 km[8][b]
Equatorial radius
25,559±4 km
4.007 Earths[8][b]
Polar radius
24,973±20 km
3.929 Earths[8][b]
Flattening 0.0229±0.0008[c]
Circumference 159,354.1 km[3]
8.1156×109 km2[3][b]
15.91 Earths
Volume 6.833×1013 km3[5][b]
63.086 Earths
Mass (8.6810±0.0013)×1025 kg
14.536 Earths[9]GM=5,793,939±13 km3/s2
Mean density
1.27 g/cm3[5][d]
8.69 m/s2[5][b]
0.886 g
0.23[10] (estimate)
21.3 km/s[5][b]
−0.71833 d (retrograde)
17 h 14 min 24 s[8]
Equatorial rotation velocity
2.59 km/s
9,320 km/h
97.77° (to orbit)[5]
North pole right ascension
17h 9m 15s
North pole declination
Albedo 0.300 (Bond)
0.51 (geom.)[5]
Surface temp. min mean max
bar level[11] 76 K (−197.2 °C)
0.1 bar
47 K 53 K 57 K
5.9[13] to 5.32[5]
3.3″ to 4.1″[5]
27.7 km[5]
Composition by volume (Below 1.3 bar)


Uranus is the only planet whose name is derived directly from a figure from Greek mythology, from the Latinised 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 solar orbit. Its north and south poles, therefore, lie where most other planets have their equators.[17] 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.[17] 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).[18]


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