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Orbit: 583,420 km from Uranus
Orbital period: 13 days
Gravity: 0.348m/s²
Diameter: 1523 km
Mass: 3.03e21 kg
Oberon, also designated Uranus IV, is the outermost major moon of the planet Uranus. It is the second largest and second most massive of the Uranian moons, and the ninth most massive moon in the Solar System.

Discovered by Herschel in 1787.

Oberon and Umbriel appear quite similar though  Oberon  is 35% larger.  All of Uranus’ large moons are a mixture of about  40-50% water ice with the rest rock, a somewhat larger fraction of rock than  Saturn’s large moons such as Rhea.

Oberon, also designated Uranus IV

Oberon’s heavily cratered surface has probably been  stable since its  formation. It has far more and larger craters than do  Ariel and Titania.  Some of the craters have rays of ejecta similar to those seen on Callisto.

Some of the crater floors are dark, perhaps covered with darker material  (dirty  water?) that upwelled into the crater.

Large faults are also seen across the entire southern hemisphere of Oberon. This  indicates some geologic activity early in Oberon’s history.

The picture above shows a mountain on the limb  that rises 6 km above its surrounds.

It is actually possible to see Uranus’s 4 largest moons with an amateur  telescope.  But it takes a very dark sky and a telescope with at least a 12 inch  (30 cm) aperture.




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