Uranus

Uranus ()

Photograph of Uranus in true colour (by Voyager 2 in 1986)
Discovery
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[10][a]
Epoch J2000
Aphelion	20.0965 AU (3006.39 Gm)
Perihelion	18.2861 AU (2735.56 Gm)
Semi-major axis	19.19126 AU (2870.972 Gm)
Eccentricity	0.04717
Orbital period	84.0205 yr 30,688.5 d[4] 42,718 Uranian solar days[5]
Synodic period	369.66 days[6]
Average orbital speed	6.80 km/s[6]
Mean anomaly	142.238600°
Inclination	0.773° to ecliptic 6.48° to Sun's equator 0.99° to invariable plane[7]
Longitude of ascending node	74.006°
Time of periastron	17–19 August 2050[8][9]
Argument of perihelion	96.998857°
Known satellites	27
Physical characteristics
Mean radius	25,362±7 km[11][b]
Equatorial radius	25,559±4 km 4.007 Earths[11][b]
Polar radius	24,973±20 km 3.929 Earths[11][b]
Flattening	0.0229±0.0008[c]
Circumference	159,354.1 km[4]
Surface area	8.1156×109 km2[4][b] 15.91 Earths
Volume	6.833×1013 km3[6][b] 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[6][d]
Surface gravity	8.69 m/s2[6][b] 0.886 g
Moment of inertia factor	0.23[13] (estimate)
Escape velocity	21.3 km/s[6][b]
Rotation period	−0.71832 d −17 h 14 m 23 s (retrograde)[5]
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
Axial tilt	97.77° (to orbit)[6]
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]
Surface temp. min mean max 1 bar level[16] 76 K (−197.2 °C) 0.1 bar (tropopause)[17] 47 K 53 K 57 K
Apparent magnitude	5.38[18] to 6.03[18]
Angular diameter	3.3″ to 4.1″[6]
Atmosphere[17][20][21][e]
Scale height	27.7 km[6]
Composition by volume	(Below 1.3 bar) Gases: 83 ± 3% hydrogen (H 2) 15 ± 3% helium (He) 2.3% methane (CH 4) 0.009% (0.007–0.015%) hydrogen deuteride (HD) hydrogen sulfide (H 2S)[19] Ices: ammonia (NH 3) water (H 2O) ammonium hydrosulfide (NH 4SH) methane hydrate

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, helium 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] Nobody knows why exactly it is. 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 days in a year on Uranus.^[23]

Uranus was discovered in 1781.^[24] This planet can be seen with the naked eye under perfect conditions. John Flamsteed saw it decades before but thought it was 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 mythology version of the Sumerian god Anu,^[25] who was a god of the sky.

1. ↑ Cite error: The named reference OED was used but no text was provided for refs named (see the help page).
2. ↑ Cite error: The named reference BBCOUP was used but no text was provided for refs named (see the help page).
3. ↑ "Uranian". Oxford English Dictionary. Oxford University Press. 2nd ed. 1989.
4. ↑ ^{4.0 4.1 4.2} Cite error: The named reference nasafact was used but no text was provided for refs named (see the help page).
5. ↑ ^{5.0 5.1} Cite error: The named reference CSeligman was used but no text was provided for refs named (see the help page).
6. ↑ ^{6.0 6.1 6.2 6.3 6.4 6.5 6.6 6.7 6.8} Cite error: The named reference fact was used but no text was provided for refs named (see the help page).
7. ↑ Cite error: The named reference Souami_Souchay_2012 was used but no text was provided for refs named (see the help page).
8. ↑ Jean Meeus, Astronomical Algorithms (Richmond, Virginia: Willmann-Bell, 1998) p271. Bretagnon's complete VSOP87 model. It gives the 17th @ 18.283075301au. http://vo.imcce.fr/webservices/miriade/?forms Archived 7 September 2021 at the Wayback Machine IMCCE Observatoire de Paris / CNRS Calculated for a series of dates, five or ten days apart, in August 2050, using an interpolation formula from Astronomical Algorithms. Perihelion came very early on the 17th. INPOP planetary theory
9. ↑ "HORIZONS Planet-center Batch call for August 2050 Perihelion". ssd.jpl.nasa.gov (Perihelion for Uranus planet-center (799) occurs on 2050-Aug-19 at 18.28307512au during a rdot flip from negative to positive). NASA/JPL. Archived from the original on 7 September 2021. Retrieved 2021-09-07.
10. ↑ Cite error: The named reference VSOP87 was used but no text was provided for refs named (see the help page).
11. ↑ ^{11.0 11.1 11.2 11.3 11.4 11.5 11.6} Cite error: The named reference Seidelmann Archinal A'hearn et al. 2007 was used but no text was provided for refs named (see the help page).
12. ↑ Cite error: The named reference Jacobson Campbell et al. 1992 was used but no text was provided for refs named (see the help page).
13. ↑ de Pater, Imke; Lissauer, Jack J. (2015). Planetary Sciences (2nd updated ed.). New York: Cambridge University Press. p. 250. ISBN 978-0521853712. Archived from the original on 26 November 2016. Retrieved 17 August 2016.
14. ↑ Cite error: The named reference Pearl_et_al_Uranus was used but no text was provided for refs named (see the help page).
15. ↑ Cite error: The named reference Mallama_et_al was used but no text was provided for refs named (see the help page).
16. ↑ Cite error: The named reference Podolak Weizman et al. 1995 was used but no text was provided for refs named (see the help page).
17. ↑ ^{17.0 17.1} Cite error: The named reference Lunine 1993 was used but no text was provided for refs named (see the help page).
18. ↑ ^{18.0 18.1} Cite error: The named reference Mallama_and_Hilton was used but no text was provided for refs named (see the help page).
19. ↑ Irwin, Patrick G. J.; et al. (23 April 2018). "Detection of hydrogen sulfide above the clouds in Uranus's atmosphere" (PDF). Nature Astronomy. 2 (5): 420–427. Bibcode:2018NatAs...2..420I. doi:10.1038/s41550-018-0432-1. hdl:2381/42547. ISSN 2397-3366. S2CID 102775371. Archived from the original (PDF) on 28 April 2019. Retrieved 25 August 2019.
20. ↑ Cite error: The named reference Lindal Lyons et al. 1987 was used but no text was provided for refs named (see the help page).
21. ↑ Cite error: The named reference Conrath Gautier et al. 1987 was used but no text was provided for refs named (see the help page).
22. ↑ Its north and south poles, therefore, lie where most other planets have their equators. Smith B.A. 1986. Voyager 2 in the Uranian system: imaging science results. Science 233 (4759): 43–64. record/ 1230972#.Xcgi81f7SUk
23. ↑ library.thinkquest.org/C005921/Uranus/uranLocOrb.htm
24. ↑ Gay, Peter; Time-Life Books (1966). "The Practical Philosophers". Age of Enlightenment. Time. p. 25.
25. ↑ Burkert 2005, p. 295. sfn error: no target: CITEREFBurkert2005 (help)