Oberon (moon)

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This article is about the Uranus moon. For other uses, see Oberon.

**Oberon**
Discovery
Image:Voyager 2 picture of Oberon.jpg Click image for description
Discovered by	William Herschel
Discovery date	January 11, 1787
Orbital characteristics
Semi-major axis	583,520 km
Mean orbit radius	583,519 km
Eccentricity	0.0014
Orbital period	13.463234 d
Inclination	0.058° (to Uranus' equator)
Satellite of	Uranus
Physical characteristics
Mean radius	761.4 km (0.1194 Earths)
Surface area	7,285,000 km²
Volume	1,849,000,000 km³
Mass	3.014×10²¹ kg (5.0455×10^-4 Earths)
Mean density	1.63 g/cm³
Equatorial surface gravity	0.346 m/s²
Escape velocity	0.73 km/s
Rotation period	presumed synchronous^[2]
Albedo	0.23
Temperature	~61 K
Apparent magnitude	13.94 ^[3]

Oberon (pronounced /ˈoʊbərɒn/ oe'-bər-on) is the outermost of the major moons of the planet Uranus. With a mean radius of about 760 km., Oberon is the second largest moon of Uranus, as well as the tenth largest moon in the solar system.

1 Discovery
2 Name
3 Physical features
4 See also
5 Notes
6 External links

Discovery

It was discovered on January 11, 1787 by William Herschel, in the same year that he reported Titania.^[4]^[5] He would later report four more satellites, which would turn out to be spurious.^[6] Remarkably, for nearly fifty years following their discovery, Titania and Oberon would not be observed by any other instrument than William Herschel's.^[7] However, the moon can be seen from Earth with a present-day amateur telescope.^[8]

Name

All of the moons of Uranus are named for characters from Shakespeare or Alexander Pope. Oberon was named after Oberon, the King of the Fairies in A Midsummer Night's Dream.

The name "Oberon" and the names of all four satellites of Uranus then known were suggested by Herschel's son John Herschel in 1852 at the request of William Lassell, who had discovered Ariel and Umbriel the year before.^[9] Lassell had earlier endorsed Herschel's 1847 naming scheme for the seven then-known satellites of Saturn and had named his newly-discovered eighth satellite Hyperion in accordance with Herschel's naming scheme in 1848. The adjectival form of the name is Oberonian.

Oberon is also now designated Uranus IV. It was initially called simply "the second satellite of Uranus"; in 1848 it was given the designation Uranus II by William Lassell, although he sometimes also used William Herschel's numbering (where Titania and Oberon are II and IV).^[10]^[11]^[12]

Physical features

So far the only close-up images of Oberon are from the Voyager 2 probe, which photographed the moon during its Uranus flyby in January, 1986. At the time of the flyby the southern hemisphere of the moon was pointed towards the Sun, so the northern hemisphere could not be studied.

Although its interior make-up is uncertain, one model suggests that Oberon is composed of roughly 50% water ice, 30% silicate rock, and 20% methane-related carbon/nitrogen compounds. It has an old, heavily cratered, and icy surface which shows little evidence of internal activity other than some unknown dark material that apparently covers the floors of many craters. However, some large faults can be seen across the southern hemisphere, which indicates some internal activity early in its life.

So far, scientists have recognised a few types of geological features on Oberon: craters, chasmata, and mountains. In fact one such mountain rises about 6 kilometers (3.7 miles) above the Oberonian surface.

Notes

^ [1]
^ An application of a rough formula indicates tidal locking on a timescale of the order of 300,000 years (see Tidal locking).
^ Classic Satellites of the Solar System. Observatorio ARVAL. Retrieved on 2007-09-28.
^ An Account of the Discovery of Two Satellites Revolving Round the Georgian Planet, Philosophical Transactions of the Royal Society of London, Vol. 77, pp. 125-129, (1787)
^ On George's Planet and its satellites, Philosophical Transactions of the Royal Society of London, Vol. 78, pp. 364-378, (1788)
^ On the Discovery of Four Additional Satellites of the Georgium Sidus; The Retrograde Motion of Its Old Satellites Announced; And the Cause of Their Disappearance at Certain Distances from the Planet Explained, Philosophical Transactions of the Royal Society of London, Vol. 88, pp. 47-79, (1798)
^ Herschel, J.; On the Satellites of Uranus, Monthly Notices of the Royal Astronomical Society, Vol. 3, No. 5 (March 14, 1834) pp. 35–36
^ http://seds.lpl.arizona.edu/nineplanets/nineplanets/oberon.html
^ http://adsabs.harvard.edu//full/seri/AN.../0034//0000169.000.html Adsabs.harvard.edu Retrieved on 05-19-07
^ Lassell, W.; Observations of Satellites of Uranus, Monthly Notices of the Royal Astronomical Society, Vol. 8, No. 3 (January 14, 1848), pp. 43–44
^ Struve, O.; Note on the Satellites of Uranus, Monthly Notices of the Royal Astronomical Society, Vol. 8, No. 3 (January 14, 1848), pp. 44–47
^ Lassell, W.; Bright Satellites of Uranus, Monthly Notices of the Royal Astronomical Society, Vol. 10, No. 6 (April 12, 1850), p. 135

External links

Oberon profile by NASA's Solar System Exploration
Oberon profile on The Nine Planets

v • d • e Uranus
Major Moons	Ariel · Miranda · Oberon · Titania · Umbriel
Characteristics	Atmosphere · Rings of Uranus · Moons
Discovery	William Herschel · William Lassell
Exploration	Voyager program · Voyager 2
Other	15 Orionis · Uranus-crosser asteroid · In fiction

v • d • e Natural satellites of the Solar System
Planetary satellites	Terrestrial · Martian · Jovian · Saturnian · Uranian · Neptunian
Other satellite systems	Plutonian · Eridian · Asteroid satellites
Largest satellites	Ganymede · Titan · Callisto · Io · Moon · Europa · Triton Titania · Rhea · Oberon · Iapetus · Charon · Umbriel · Ariel · Dione · Tethys · Enceladus · Miranda · Proteus · Mimas
Inner satellites · Trojans · Irregulars · List · List by diameter · Timeline of discovery · Naming