Uranus is the third largest planet, being slightly under half the size of the second largest, Saturn, and a mere 3,000 km larger than the next largest, Neptune. However, it is twice as far away as Saturn, so it appears as only a quarter of the diameter of Saturn.
With even less sunlight at this distance, and without the benefit of Saturn's beautiful ring system to reflect sunlight, Uranus is barely visible to the naked eye. It is therefore little surprise that it was not discovered until after the invention of the telescope - William Herschel discovered it by accident with a telescope in his garden in Bath, England.
It common with the outer giant planets, Uranus is a "gas giant" and has no solid surface. In fact it shows a uniformly bland appearance - even Voyager 2 struggled to see any detail in its pale blueish-green atmosphere. It is unusual though in that some ancient collision has tipped the planet on its side, so its pole lie almost in the plane of its orbit, where you would expect the equator to be.
Uranus has 5 major moons, Miranda, Ariel, Umbriel, Titania and Oberon, named after characters in Shakespeare's plays, but all are hard to see in amateur telescopes.
| Distance from Sun (Million km): | 2,742 (min) | 3,008 (max) |
| Orbital Period: | 84 years | |
| Mean Interval between Oppositions: | 370 days | |
| Diameter (km): | 52,000 (equatorial) | 49,000 (polar) |
| Rotation Period: | 16 to 28h (backwards) | |
| Apparent Diameter (arc seconds): | 3.9 | |
| Max. Apparent Brightness (magnitude): | +5.5 |
|
|
Jet Propulsion Laboratory Uranus pages | |
|
|
|
|