# Uranus and Neptune

Uranus and Neptune are the the planets that are almost the farthest from the sun. (Pluto is the farthest, but it is exceptional in its properties.)

Uranus orbits the sun with

• a = 19 AU
• P = 84 yr
Neptune orbits the sun with
• a = 30 AU
• P = 160 yr
For Uranus,
• Mass is 15 times the mass of the earth.
• Radius is 4.0 times the radius of the earth.
This gives a density of about 16/(4)3*(density)E ~ 0.25 (density)E. More precisely, the density is 1300 kg/m3.

For Neptune,

• Mass is 17 times the mass of the earth.
• Radius is 3.9 times the radius of the earth.
This gives a density of about 16/(4)3*(density)E ~ 0.25 (density)E. More precisely, the density is 1600 kg/m3.

Thus Uranus and Neptune may be expected to be similar inside, something like

• H and He gas on the outside
• H2O and some N H3 and CH4 liquid most of the way through. (Fix says ``water and rock'').
• a molten rock core.

Here is a picture of Uranus . Here is a picture of Neptune.

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Davison E. Soper, Institute of Theoretical Science, University of Oregon, Eugene OR 97403 USA soper@bovine.uoregon.edu