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Line 4: − + − + − + − + − + − + − + − + − + − + − + − + − + − + − + − + − + − + − + + + + − + − The name "Uranus" was first proposed by Bode<ref>http://www.nineplanets.org/help.html#bode</ref> in conformity with the other planetary names from classical mythology but didn't come into common use until 1850. Uranus has been visited by only one spacecraft, Voyager 2 in January 1986.+ + − One fascinating feature of Uranus is that it is tipped over. Its north pole lies 98° from being up and down on it's orbit plane. The seasons are therefore extreme, the sun rises at the north pole and says up for 42 years. When it sets there are 42 years of darkness. There is also a series of 9 narrow rings surrounding Uranus like many of the other gas giant planets. <ref>Universe, 7th Edition by R.A. Freedman & W.J. Kaufmann </ref>+ + − + − + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +
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|symbol=Uranus symbol.svg
|symbol=Uranus symbol.svg
|order=8
|order=8
|date=1781
|date=March 13, 1781<ref name=usgs>"[http://planetarynames.wr.usgs.gov/append7.html Gazetteer of Planetary Nomenclature: Planetary Body Names and Discoverers]." US Geological Survey, Jennifer Blue, ed. March 31, 2008. Accessed April 17, 2008.</ref>
|discname=[[William Herschel]]
|discname=William Herschel<ref name=usgs/>
|origname=Roman (and Greek) name for heaven
|origname=Roman (and Greek) name for heaven and father of Saturn.<ref name=usgs/>
|primary=Sun
|primary=Sun
|periapsis=18.286 AU
|periapsis=18.286 AU
|apoapsis=20.096 AU
|apoapsis=20.096 AU
|semimajor=19.191 AU<ref>http://www.nineplanets.org/uranus.html</ref>
|semimajor=19.191 AU<ref name=Arnett>Arnett, Bill. "[http://www.nineplanets.org/uranus.html Uranus]." <http://www.nineplanets.org/> Accessed January 22, 2008.</ref>
|bode=19.6 AU
|bode=19.6 AU
|circumference=120.515 AU
|circumference=120.515 AU
|eccentricity=0.046
|eccentricity=0.046
|sidereal=84.07 a
|sidereal=84.0016846 a<ref name=ssdhoriz>"[http://ssd.jpl.nasa.gov/horizons.cgi HORIZONS on Uranus]." ''Solar System Dynamics'', Jet Propulsion Laboratory, NASA, August 7, 2007. Accessed April 25, 2008.</ref>
|synodic=369.65 da (1.012 a)
|synodic=369.65 da
|orbitspeed=6.795 km/s
|orbitspeed=6.8352 km/s<ref name=ssdhoriz/>
|inclination=0.744°
|inclination=0.744°
|reference=the ecliptic
|reference=the ecliptic
|siderealday=-17.15416667 h (-0.715 da)<ref>http://www.solarviews.com/eng/uranus.htm</ref>
|siderealday=-17.24 h<ref name=ssdhoriz/>
|axialtilt=97.86°
|axialtilt=97.86°<ref name=ssdhoriz/>
|mass=8.6832 * 10<sup>25</sup> kg (14.52 * earth)
|mass=8.6832 * 10<sup>25</sup> kg (14.53 * earth)<ref name=ssdhoriz/>
|density=1,270 kg/m³
|density=1,318 kg/m³<ref name=ssdhoriz/>
|surfacegrav=7.77 m/s² (25.492 ''g'')
|surfacegrav=8.69 m/s²<ref name=ssdhoriz/>
|escapespeed=21.30 km/s
|escapespeed=21.30 km/s<ref name=ssdhoriz/>
|equatorradius =25,559 km
|meanradius=25,362 km<ref name=ssdhoriz/>
|surfacearea=8,084,000,000 km² (15.849 * earth)
|equatorradius =25,559 km<ref name=ssdhoriz/>
|meantemp=68 K
|polarradius=24,973 km<ref name=ssdhoriz/>
|moons=22
|surfacearea=8,084,000,000 km²
|composition=83% hydrogen, 15% helium and 2% methane<ref>http://www.nineplanets.org/uranus.html</ref>
|meantemp=76 K<ref name=ssdhoriz/>
|albedo=0.51
|moons=27
|composition=83% hydrogen, 15% helium and 2% methane<ref name=Arnett/>
|color=blue-green
|albedo=0.51<ref name=ssdhoriz/>
}}
}}
'''Uranus''' is the seventh planet in the Solar System. Uranus was discovered by the English astronomer [[William Herschel]] in 1781. It was originally named "Georgium Sidis," or "George's Planet," in honor of King George III of England. The name was later changed and named after the ancient Greek god of the heavens who was the father of [[Saturn]] (Chronos) and grandfather of [[Jupiter]] (Zeus). Uranus has twenty one moons, 5 of which are large enough to determine their existence from earth. The moons include Miranda, Circe, Puck, Baltar, Spungo, and Tybalt. Most of the moons of Uranus have names drawn from the works of [[William Shakespeare|Shakespeare]].
'''Uranus''' is the seventh [[member of::planet]] from the [[sun]], and the third largest. It is named after the father of Greek (and Roman) gods, who also happens to be the god of the sky. Uranus is a [[gas giant]], but despite its great size compared to the [[terrestrial planet| terrestrial planets]], it was not discovered until 1781 by William Herschel, who used a telescope.
== Orbital characteristics ==
Uranus' average distance from the sun (semi-major axis) is 19.1 AU, which is close to the 19.6 AU predicted by the [[Titius-Bode Law]]. Its sidereal year is 84.02 [[Earth]] years. The orbital excentricity is 0.046, which is nearly circular (though the orbit of Earth is more circular still). Uranus' orbit is very slightly inclined to the plane of the ecliptic; in fact its orbital inclination with respect to the ecliptic is the least of those of all the planets.
== Rotational characteristics ==
Uranus' sidereal day is 17.24 Earth hours. Uranus' rotation is ''retrograde'' with respect to its orbit around the Sun and the orbits of most of the other planets. Moreover its axis is tilted 97.86° with respect to its orbital plane, so that in a sense the planet is rolling on its side.
==Notes & References==
The planet has a magnetic field, whose axis is oriented 60° away from its rotational axis and, furthermore, does not intercept the planet's center.
<references/>
== Physical characteristics ==
The planet’s radius is 25,559 km (15,882 miles). Uranus’s atmosphere is about 83 % [[hydrogen]], 15% [[helium]], and 2% [[methane]]. The methane, more than any other constituent, gives Uranus its color. Uranus' atmosphere is relatively featureless; even [[Voyager 2]] did not resolve many more features than can be seen through an earthbound telescope.
==Difficulties for naturalistic theories==
=== Formation of the planet ===
The [[nebular hypothesis]] would not even have allowed Uranus and its twin, [[Neptune]], to form at its tremendous distance from the [[Sun]] in the time generally allotted. As the journal ''Astronomy'' stated the problem:{{cquote|Pssst … astronomers who model the formation of the solar system have kept a dirty little secret: Uranus and Neptune don’t exist. Or at least computer simulations have never explained how planets as big as the two gas giants could form so far from the sun. Bodies orbited so slowly in the outer parts of the sun’s protoplanetary disk that the slow process of gravitational accretion would need more time than the age of the solar system to form bodies with 14.5 and 17.1 times the mass of Earth.}} <ref>R.N., Birth of Uranus and Neptune, ''Astronomy'' '28'(4):30, 2000</ref>
Of course, the time allotted for the formation of the [[solar system]] is generally taken to be the alloted age of the [[Earth]]. In theory, the solar system could be older than the earth itself, but not much older. The solar system has other bodies in it that are much "younger." Nor does the above account for the [[young solar system evidence|body of evidence]] that the solar system is in fact quite young.
=== Orientation of the Uranian system ===
According to evolutionary theories of how the Solar System formed (i.e. the [[nebular hypothesis]]), Uranus' axis should not be tilted 98 degrees with respect to its orbit. Moreover its moons orbit Uranus around its equator, like the hands of a clock around a clock face. Uranus' ten rings also are around its equator, so they look vertical. The nebular hypothesis predicts none of these observations.
Naturalistic [[Astronomy|astronomers]] theorize that Uranus originally formed upright, but suffered a collision with another object, producing its severe tilt. This, however, raises more questions:
# Why is its orbit less eccentric than those of all the other planets except only those of [[Venus]], [[Neptune]], and [[Earth]]?
# Why is Uranus' orbit less inclined to the ecliptic than is that of any planet except Earth?
# Why are the orbits of Uranus' moons so slightly inclined with respect to Uranus' present equator?<ref name=AiG>Psarris, Spike. "[http://www.answersingenesis.org/creation/v24/i3/uranus.asp Entry for Uranus]." ''[[Creation (magazine)|Creation]]'', 24(3):38-40, June 2002. Now hosted by [[Answers in Genesis]]. Accessed April 25, 2008.</ref> Indeed, the vertical orientation of Uranus' moons and of some of its rings was already well-known to astronomers before the Voyager 2 flyby. If the moons formed before the collision, then another series of precisely timed collisions would have been required to change the azimuths of all the orbits, ''and'' the rings—an absurd violation of [[Occam's razor]]. And if they formed after the collision, then in the absence of any condensing gas cloud, they ought to be inclined at random.
Naturalists try to explain that last by suggesting that Uranus' moons are leftover debris from the collision that tilted its axis. However, Uranus' moons make up only one hundredth of one percent of the mass of the planet, and an impact violent enough to knock the giant over would have produced far more debris than that. (Earth's [[Moon]], also supposed to be the result of a giant collision involving its primary, has a mass of 1.23% that of earth.)<ref name=AiG/><ref name=Psarris>Psarris, Spike. ''[[Our Created Solar System]]'' Seattle Creation Conference, 2006.</ref> Moreover, not only are the moons of Uranus oriented well to Uranus' equator, but many of them orbit retrograde to Uranus' own rotation.
=== The magnetic field ===
As mentioned, Uranus' magnetic axis is 60 degrees displaced from Uranus' axis of rotation, and the axis also does not intercept the planet's center. Moreover the strength of Uranus' magnetic field presented another problem for the evolutionary model when Voyager 2 flew by the planet in 1986; however, it did not surprise creationists, as Dr. Russell Humphreys predicted its strength based on the creation model two years before Voyager flew by.
=== Radiation of energy ===
The other three gas giants ([[Jupiter]], [[Saturn]], and [[Neptune]]) radiate more energy than they absorb from the Sun. Uranus does not. Yet Uranus and Neptune are of comparable size, mass, atmospheric composition, and length of the sidereal day. No naturalistic theory can account for this salient difference. Uranus' peculiar lack of an internal heat source was known before Voyager and confirmed by Voyager.<ref name=AiG/><ref name=Psarris/><ref name=Henry>Henry, Jonathan. "[http://www.answersingenesis.org/tj/v15/i3/uranus_energy.asp The energy balance of Uranus: implications for special creation]." [[Journal of Creation]] (formerly ''TJ''), 15(3):85-91, December, 2001. Hosted by [[Answers in Genesis]]. Accessed April 25, 2008.</ref>
== Satellites ==
Uranus has twenty-seven named satellites and a number of concentric rings. The orbits of its satellites are slightly inclined to Uranus' own equator. Remarkably, many of the revolutions of Uranus' moons are retrograde.
== Missions to Uranus ==
The only deep-space probe to visit Uranus thus far has been [[Voyager 2]], which flew by Uranus on January 24, 1986. Voyager 2 discovered ten of Uranus' twenty-seven satellites, and two previously unknown rings. Voyager 2 then continued onward to [[Neptune]] before heading out of the [[solar system]].
== References ==
{{reflist|2}}
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