Uranus Seventh planet from the Sun Discovered in 1781 Sidereal Period: 83.75 years Sidereal Day: 0.72 days Average Surface Temperature: 58 K (-355 F) 17 Moons
Uranus 4.01 x the radius of Earth 0.23 x the density of Earth Solid core Ice/rock layer Liquid hydrogen
Neptune Eighth planet from the Sun Discovered in 1845/1846 Sidereal Period: 163.7 years Sidereal Day: 0.67 days Average Surface Temperature: 59 K (-353 F) 8 Moons
Neptune 3.88 x the radius of Earth 0.297 x the density of Earth Solid core Ice/rock layer Liquid hydrogen
Comparing the Outer Planets