Ariel (moon)
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| Discovery | |
|---|---|
| Discovered by: | William Lassell |
| Discovery date: | October 24, 1851 |
| Orbital characteristics | |
| Semi-major axis: | 191,020 km |
| Mean radius of orbit: | 190,900 km |
| Eccentricity: | 0.0012 |
| Orbital period: | 2.520 d |
| Inclination: | 0.260° (to Uranus' equator) |
| Satellite of: | Uranus |
| Physical characteristics | |
| Dimensions: | 1162.2 × 1155.8 × 1155.4 km |
| Mean radius: | 578.9 km (0.0908 Earths) |
| Surface area: | 4,211,300 km² |
| Volume: | 812,600,000 km³ |
| Mass: | 1.35×1021 kg (2.26×10-4 Earths) |
| Mean density: | 1.67 g/cm³ |
| Equatorial surface gravity: | 0.27 m/s2 |
| Escape velocity: | 0.56 km/s |
| Rotation period: | synchronous |
| Albedo: | 0.39 |
| Temperature: | ~58 K |
Ariel (air'-ee-əl, IPA /ˈɛəriəl/) is a moon of Uranus discovered on 24 October 1851 by William Lassell. It was discovered at the same time as Umbriel.
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[edit] Name
Ariel is named after the leading sylph in Alexander Pope's poem Rape of the Lock. It is also the name of the spirit who serves Prospero in Shakespeare's Tempest.
The name "Ariel" and the names of all four satellites of Uranus then known were suggested by John Herschel in 1852 at the request of Lassell ([1]). 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 Arielian.
It is also designated Uranus I.
[edit] Physical characteristics
- See also: List of geological features on Ariel
The first and so far only close-up observations of Ariel were made by the Voyager 2 probe during its 1986 Uranus fly-by. Voyager 2 made its closest approach of Ariel on January 24, 1986 and passed within 127,000 km of the moon.[1] Because the moon's south pole was pointed towards the Sun, only the southern hemisphere was photographed.
Ariel's composition is roughly 70% ices (water ice, carbon dioxide ice, and possibly methane ices) and 30% silicate rock, and it appears to have regions of fresh frost in places, particularly in the ejecta radiating from young impact craters. The oldest and most extensive geologic unit observed on Ariel by Voyager 2 was a vast area of cratered plains centered near Ariel's south pole. Analysis of craters seen on Ariel's cratered plains suggest most are younger than many of those seen on Titania, Oberon, and Umbriel.[2] The largest crater observed on Ariel is Yangoor, at only 78 km across, and shows signs of deformation since its formation. Voyager 2 also observed a network of faults, canyons, and icy outflows running along Ariel's mid-southern latitudes, breaking up the cratered plains region. Smooth material and grooves are often seen running down length of Ariel's valley networks, suggested that some canyon floors have been covered in warm ice extruded from Ariel's interior.[2]
Official names have been given to the following geological feature types on Ariel:
[edit] Trivia
- On July 26, 2006, the Hubble Space Telescope captured a rare transit made by Ariel across the face of Uranus, during which the satellite cast a shadow that could be seen on the Uranian cloudtops. Such events are rare and only occur during an equinox, as the planet's axis is tilted 98° to the plane of the Solar System.
[edit] See also
[edit] Notes and references
- ^ Voyager Mission Description. Accessed May 29, 2006
- ^ a b B. A. Smith et al. (1982). "Voyager 2 in the Uranian system - Imaging science results". Science 233: 43-64.
[edit] External links
- William Lassell, Astronomical Journal 2 (1851) 70
- AN, 33 (1852) 257/258
- AN, 34 (1852) 325/326
- Ariel basemap derived from Voyager images
- NASA Archive of publically released Ariel images
| Moons of Uranus | |
|---|---|
| Inner | Cordelia · Ophelia · Bianca · Cressida · Desdemona · Juliet · Portia · Rosalind · Cupid · Belinda · Perdita · Puck · Mab |
| Major (spheroid) | Miranda · Ariel · Umbriel · Titania · Oberon |
| Outer (irregular) | Francisco · Caliban · Stephano · Trinculo · Sycorax · Margaret · Prospero · Setebos · Ferdinand |
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See also Rings of Uranus
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| 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 |
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