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Uranus, as seen by Voyager 2
|Discovered by||William Herschel|
|Discovery time||March 13, 1781|
|Reference date J2000|
|Longest distance from the Sun||
3 004 419 704 km|
20.083 305 26 AU
|Shortest distance from the Sun||
2 748 938 461 km|
18.375 518 63 AU
|Longest distance from the center of its orbital path
2 876 679 082 km|
19.229 411 95 AU
|How egg-shaped its orbit is
|0.044 405 586|
|How long it takes to complete an orbit||
30 799.095 days|
84.323 326 yr
|How long an orbit seems to take
(from the central body)
|Average speed||6.81 km/s|
|Mean anomaly||142.955 717°|
|Angle above the reference plane
6.48° to Sun's equator
|Longitude of where it comes up through the reference plane||73.989 821°|
|Angle between its shortest distance from what it orbits around and where it comes up through the reference plane
("argument of periapsis")
|Natural things which orbit around it||27|
|Size and Other Qualities|
|Distance from its center to its surface at its equator||
25 559 ± 4 km|
|Distance from its center to its surface at the poles||
24 973 ± 20 km|
|Flatness at the poles||0.022 9 ± 0.000 8[b]|
|Area of its surface||
8.115 6×109 km²[c]|
|Volume inside it||
|Mass||GM=5 793 939 ± 13 km³/s²|
|Average density||1.27 g/cm³[c]|
|Gravity at its surface||
|Slowest speed able to escape into space
|How long it takes to turn around one time
(in relation to the stars)
−0.718 33 day|
17 h 14 min 24 s
|Angle at which it turns
(in relation to its orbit)
|Long. around the celestial equator
17 h 9 min 15 s|
|Angle above the celestial equator
|How much light it reflects||
|5.9 to 5.32|
|Scale height||27.7 km|
(Below 1.3 bar)
| colspan="2" |
| width="100%" style="padding: 5px; background: #FCFCFC; border: 1px #AAA solid;"
! colspan="2" style="text-align: center; font-size: 1.2em; padding: 5px;" | Elements
! width="50%" | Hydrogen (H2)
| width="50%" | 83 ± 3%
| 15 ± 3%
! Hydrogen deuteride (HD)
Uranus is the seventh planet from the Sun in the Solar System. It is a gas 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 degrees C (79 K) near the top of its atmosphere, but its small solid core (about 55% the mass of Earth) is probably about 5,000K. The planet is tilted on its axis so much that it is sideways.
This planet can be seen with the eye under perfect conditions. Some evidence suggests that this planet was catalogued as a star (34 Tauri) before its confirmed discovery.[source?]
Uranus is covered in blue clouds. The clouds, made of methane, are difficult to see as they are low in the atmosphere. There are also violent storms on the surface with winds that blow at 160 miles per hour. Scientists are studying the clouds to try and understand the storms on the planet.
The planet Uranus has a system made of 13 rings between the more extensive set around Saturn and the simpler systems around Jupiter and Neptune. The rings of Uranus were discovered in 1977. More than 200 years ago, William Herschel also reported observing rings, but modern astronomers do not believe that he saw them, because they are very dark and faint. Two additional rings were discovered in 1986 in images taken by the Voyager 2, and two outer rings were found in 2003–2005 by the Hubble Space Telescope. The rings are probably mainly composed of water.
The rings of Uranus are thought to be relatively young, not more than 600 million years old. The Uranian ring system probably began from the collisional fragmentation of moons that once existed around the planet. After colliding, the moons probably broke up into many particles, which survived as narrow, optically dense rings only in zones of maximum stability.
The ring system of Uranus has thirteen distinct rings. In order of increasing distance from the planet they are: 1986U2R/ζ, 6, 5, 4, α, β, η, γ, δ, λ, ε, ν, μ rings. They can be divided into three groups: nine narrow main rings (6, 5, 4, α, β, η, γ, δ, ε), two dusty rings (1986U2R/ζ, λ) and two outer rings (μ, ν). The rings of Uranus consist mainly of macroscopic particles and little dust, although dust is known to be present in 1986U2R/ζ, η, δ, λ, ν and μ rings.
In addition to these well-known rings, there may be numerous optically thin dust bands and faint rings between them. These faint rings and dust bands may exist only temporarily. Some of them became visible during a series of ring plane-crossing events in 2007. A number of dust bands between the rings were observed in forward-scattering [a] geometry by Voyager 2. All rings of Uranus show azimuthal brightness variations.
The rings are made of an extremely dark material. The rings are slightly red in the ultraviolet and visible parts of the spectrum and grey in near-infrared. They show no identifiable spectral features. The chemical composition of the ring particles is not known. However, they cannot be made of pure water ice like the rings of Saturn because they are too dark, darker than the inner moons of Uranus. This shows that they are probably composed of a mixture of the ice and a dark material. The nature of this material is not clear, but it may be organic compounds considerably darkened by the charged particle irradiation from the Uranian magnetosphere. The rings' particles may consist of a heavily processed material which was initially similar to that of the inner moons.
As a whole, the ring system of Uranus is unlike either the faint dusty rings of Jupiter or the broad and complex rings of Saturn, some of which are composed of very bright material—water ice. However, there are similarities with some parts of the latter ring system; the Saturnian F ring and the ε ring are both narrow, relatively dark and are shepherded by a pair of moons. The newly discovered outer rings of Uranus are similar to the outer G and E rings of Saturn. Narrow ringlets existing in the broad Saturnian rings also resemble the narrow rings of Uranus. In addition, dust bands observed between the main rings of Uranus may be similar to the rings of Jupiter. In contrast, the Neptunian ring system is quite similar to that of Uranus, although it is less complex, darker and contains more dust. The Neptunian rings are also positioned further from the planet.
Orbit and rotation
Uranus revolves around the Sun once every 84 Earth years. Its average distance from the Sun is roughly 3 billion km (about 20 AU). The intensity of sunlight on Uranus is about 1/400 that on Earth. Its orbital elements were first calculated in 1783 by Pierre-Simon Laplace. With time, discrepancies began to appear between the predicted and observed orbits, and in 1841, John Couch Adams first proposed that the differences might be due to the gravitational tug of an unseen planet. In 1845, Urbain Le Verrier began his own independent research into Uranus's orbit. On September 23, 1846, Johann Gottfried Galle located a new planet, later named Neptune, at nearly the position predicted by Le Verrier.
The rotational period of the interior of Uranus is 17 hours, 14 minutes, clockwise (retrograde). As on all giant planets, its upper atmosphere experiences very strong winds in the direction of rotation. At some latitudes, such as about two-thirds of the way from the equator to the south pole, visible features of the atmosphere move much faster, making a full rotation in as little as 14 hours.
- Williams, Dr. David R. (January 31, 2005). "Uranus Fact Sheet". NASA. http://nssdc.gsfc.nasa.gov/planetary/factsheet/uranusfact.html. Retrieved 2007-08-10.
- Yeomans, Donald K. (July 13, 2006). "HORIZONS System". NASA JPL. http://ssd.jpl.nasa.gov/?horizons. Retrieved 2007-08-08. — At the site, go to the "web interface" then select "Ephemeris Type: ELEMENTS", "Target Body: Uranus Barycenter" and "Center: Sun".
- Seidelmann, P. Kenneth; Archinal, B. A.; A’hearn, M. F.; et al. (2007). "Report of the IAU/IAGWorking Group on cartographic coordinates and rotational elements: 2006". Celestial Mech. Dyn. Astr. 90: 155–180. . http://adsabs.harvard.edu/doi/10.1007/s10569-007-9072-y.
- Munsell, Kirk (May 14, 2007). "NASA: Solar System Exploration: Planets: Uranus: Facts & Figures". NASA. http://solarsystem.nasa.gov/planets/profile.cfm?Object=Uranus&Display=Facts. Retrieved 2007-08-13.
- Jacobson, R.A.; Campbell, J.K.; Taylor, A.H.; Synnott, S.P. (1992). "The masses of Uranus and its major satellites from Voyager tracking data and Earth-based Uranian satellite data". The Astronomical Journal 103 (6): 2068–2078. . http://adsabs.harvard.edu/abs/1992AJ....103.2068J.
- Fred Espenak (2005). "Twelve Year Planetary Ephemeris: 1995 - 2006". NASA. http://sunearth.gsfc.nasa.gov/eclipse/TYPE/TYPE.html. Retrieved 2007-06-14.
- Podolak, M.; Weizman, A.; Marley, M. (1995). "Comparative models of Uranus and Neptune". Planet. Space Sci. 43 (12): 1517–1522. . http://adsabs.harvard.edu/abs/1995P%26SS...43.1517P.
- Lunine, Jonathan. I. (1993). "The Atmospheres of Uranus and Neptune". Annual Review of Astronomy and Astrophysics 31: 217–263. . http://adsabs.harvard.edu/abs/1993ARA%26A..31..217L.
- Feuchtgruber, H.; Lellouch, E.; B. Bezard; et al. (1999). "Detection of HD in the atmospheres of Uranus and Neptune: a new determination of the D/H ratio". Astronomy and Astrophysics 341: L17–L21. http://adsabs.harvard.edu/abs/1999A%26A...341L..17F.
- Lindal, G.F.; Lyons, J.R.; Sweetnam, D.N.; et al. (1987). "The Atmosphere of Uranus: Results of Radio Occultation Measurements with Voyager 2". J. Of Geophys. Res. 92: 14,987–15,001. . http://adsabs.harvard.edu/abs/1987JGR....9214987L.
- B. Conrath et al. (1987). "The helium abundance of Uranus from Voyager measurements". Journal of Geophysical Research 92: 15003–15010. . http://adsabs.harvard.edu/abs/1987JGR....9215003C.
- "The Practical Philosophers". Age of Enlightenment. Time. 1966. pp. 25.
- Faure, Gunter; Mensing, Teresa (2007). "Uranus: What Happened Here?". Introduction to Planetary Science. Ed. Faure, Gunter; Mensing, Teresa M.. Springer Netherlands. DOI:10.1007/978-1-4020-5544-7_18.
- "Uranus". nineplanets.org. http://www.nineplanets.org/uranus.html. Retrieved 2007-07-03.
- "Uranus Clouds, overview". windows.ucar.edu. http://www.windows.ucar.edu/tour/link=/uranus/atmosphere/U_clouds_overview.html. Retrieved 29 March 2010.
- "SPACE.com -- New Images Reveal Clouds on Planet Uranus". space.com. http://www.space.com/scienceastronomy/uranus_images_041110.html. Retrieved 29 March 2010.
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- "NASA's Hubble discovers new rings and moons around Uranus". Hubblesite. 2005. http://hubblesite.org/newscenter/archive/releases/2005/33/. Retrieved June 9, 2007.
- de Pater, Imke; Hammel H B. et al (2007). "The dark side of the rings of Uranus". Science 317 (5846): 1888–1890. . . http://adsabs.harvard.edu/abs/2007Sci...317.1888D.
- Baines, Kevin H. et al (1998). "Near-Infrared absolute photometric imaging of the Uranian system". Icarus 132: 266–284. . http://adsabs.harvard.edu/abs/1998Icar..132..266B.
- "Next Stop Uranus". 1986. http://www.astrosociety.org/education/publications/tnl/04/04.html. Retrieved June 9, 2007.
- George Forbes (1909). "History of Astronomy". http://www.vinnysa1store.com/historyofastronomy2.html#8. Retrieved August 7, 2007.
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- Peter J. Gierasch and Philip D. Nicholson (2004). "Uranus". NASA World Book. http://www.nasa.gov/worldbook/uranus_worldbook.html. Retrieved June 9, 2007.[dead link]
- NASA's Uranus fact sheet
- Uranus Profile by NASA's Solar System Exploration
- Keck pictures of Uranus show best view from the ground — Press release with some photographs showing rings, satellites and clouds
- News reports of December 22, 2005 rings and moons discovery
- Planets—Uranus A kid's guide to Uranus.
The Solar System
☾ = moon(s) ∅ = rings
|Mercury||Venus||Earth ☾||Mars ☾|
|Jupiter ☾ ∅||Saturn ☾ ∅||Uranus ☾ ∅||Neptune ☾ ∅|
|Dwarf planets||Ceres||Pluto ☾||Haumea ☾||Makemake|
| Groups and families: Vulcanoids · Near-Earth asteroids · Asteroid belt |
Jupiter Trojans · Centaurs · Neptune Trojans · Asteroid moons · Meteoroids · Pallas · Juno · Vesta · Hygiea · Interamnia · Europa
|See also the list of asteroids.|
|Kuiper belt – Plutinos: Orcus · Ixion – Cubewanos: Varuna · |
Quaoar · Huya
|Scattered disc: Sedna|
|Comets|| Periodic comets and non-periodic comets |
Damocloids · Oort cloud
|See also the list of solar system objects|