The Outer Gas Giants

Saturn

	Saturn	Uranus	Neptune
Mass (Jupiter Masses)	0.30	0.045	0.053
Radius (Jupiter Radii)	0.85	0.36	0.35
Average Density (kg/m³)	690	1270	1640
Distance from Sun (AU)	9.5	19.2	30.1
Equilibrium Temperature (K)	80	60	45
Observed Temperature (K)	95	60	60

All visited by Voyager 2 probe in late 1980s;
Saturn also visited by Cassini/Huygens in 2004/5

Saturn:

Clouds patterns visible
Very prominant ring system (we will return to this)
Many moons (biggest is Titan)
Rotation period: 10.6 hours

Uranus:

Accidently discovered by William Herschel in 1781
Featureless disk -- few, very faint markings
Faint rings (discovered in 1977 by occultation)
Many moons (5 relatively large, many much smaller)
Rotation axis lies in orbital plane -- "on its side''! (Impact?)
Rotation period: 17.3 hours (determined by Voyager)

Neptune:

1846: Position predicted by gravitational calculations, found w/in hours!
Cloud patterns visible
Faint rings (arclets, actually)
Moons (Triton, similar in size to our Moon, plus many smaller moons)
Rotation period: 19.2 hours