Editing Oberon (moon) (section)

== Orbit ==
Oberon orbits Uranus at a distance of about 584,000&nbsp;km, being the farthest from the planet among its five major moons.{{efn|name=five major moons}} Oberon's orbit has a small [[orbital eccentricity]] and [[orbital inclination|inclination]] relative to the [[equator]] of Uranus.<ref name="orbit" /> Its orbital period is around 13.5&nbsp;days, coincident with its [[rotational period]]. In other words, Oberon is [[tidally locked]], with one face always pointing toward the planet.<ref name="Smith Soderblom et al. 1986" /> Oberon spends a significant part of its orbit outside the Uranian [[magnetosphere]].<ref name="Ness Acuña et al. 1986" /> As a result, its surface is directly struck by the [[solar wind]].<ref name="Grundy Young et al. 2006" /> This is important, because the trailing hemispheres of satellites orbiting inside a magnetosphere are struck by the magnetospheric plasma, which co-rotates with the planet.<ref name="Ness Acuña et al. 1986" /> This bombardment may lead to the darkening of the trailing hemispheres, which is actually observed for all Uranian moons except Oberon (see below).<ref name="Grundy Young et al. 2006" />

Because Uranus orbits the Sun almost on its side, and its moons orbit in the planet's equatorial plane, they (including Oberon) are subject to an extreme seasonal cycle. Both northern and southern [[Poles of astronomical bodies#Geographic poles|poles]] spend 42 years in a complete darkness, and another 42 years in continuous sunlight, with the sun rising close to the [[zenith]] over one of the poles at each [[solstice]].<ref name="Grundy Young et al. 2006" /> The ''Voyager 2'' flyby coincided with the southern hemisphere's 1986 summer solstice, when nearly the entire northern hemisphere was in darkness. Once every 42 years, when Uranus has an [[equinox]] and its equatorial plane intersects the Earth, mutual [[occultation]]s of Uranus's moons become possible. One such event, which lasted for about six minutes, was observed on May 4, 2007, when Oberon occulted Umbriel.<ref name="Hidas Christou et al. 2008" />