Changes

|meantemp=76 K<ref name=ssdhoriz/>

|meantemp=76 K<ref name=ssdhoriz/>

|moons=27

|moons=27

|composition=83% hydrogen, 15% helium and 2% methane<ref name=Arnett/>

|composition=83% [[hydrogen]], 15% [[helium]] and 2% [[methane]]<ref name=Arnett/><ref name=rst>Short, Nicholas M., Sr. "[http://rst.gsfc.nasa.gov/Sect19/Sect19_20.html Uranus and Neptune, and their Satellites; the Pluto dwarfs]." Remote Sensing Tutorial, Goddard Space Flight Center, [[NASA]]. Accessed April 30, 2008.</ref>

|color=blue-green

|color=blue-green

|albedo=0.51<ref name=ssdhoriz/>

|albedo=0.51<ref name=ssdhoriz/>

== Physical characteristics ==

== Physical characteristics ==

Uranus is a [[gas giant]] having a radius of 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.

Uranus is a [[gas giant]] having a radius of 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.<ref name=rst/>

 

[[Voyager 2]] did not resolve many more features than can be seen through an ordinary earthbound telescope. But seven years of observation by the [[Hubble Space Telescope]] have shown that Uranus' atmosphere is quite active. It has even developed a visible storm (the dark spot), which Voyager 2 did not capture.

 

Uranus has a total of thirteen rings. The brightest of these is the epsilon ring, which was until recently assumed to be the outermost. However, the Hubble telescope team subsequently discovered three more rings lying much further out from Uranus, together with another inner satellite, [[Mab]], closely associated with one of them.

==Difficulties for naturalistic theories==

==Difficulties for naturalistic theories==

=== Orientation of the Uranian system ===

=== 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.

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' thirteen 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:

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:

== Missions to Uranus ==

== 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]].

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 ==

== References ==