 Cassini image of Pallene transiting Saturn on October 16, 2010 | |
| Discovery | |
|---|---|
| Discovered by | Voyager 2 (first discovery) Cassini Imaging Team[1] |
| Discovery date | June 1, 2004 (second discovery byCassini-Huygens) |
| Designations | |
Designation | Saturn XXXIII |
| Pronunciation | /pəˈliːniː/[2] |
Named after | ΠαλλήνηPallēnē |
| S/1981 S 14 (first discovery) S/2004 S 2 (second discovery) | |
| Adjectives | Pallenean/pæləˈniːən/[3] |
| Orbital characteristics[4] | |
| Epoch 20 June 2004 (JD 2453177.5) | |
| 212300 km[5] | |
| Eccentricity | 0.004[5] |
| 1.156059 d[5] | |
| Inclination | 0.1810°±0.0014° (to Saturn's equator) |
| Satellite of | Saturn |
| Group | Alkyonides |
| Physical characteristics | |
| Dimensions | 5.76 × 4.16 × 3.68 km (± 0.14 × 0.14 × 0.14 km)[6]: 2 |
| 4.46±0.14 km[6]: 2 | |
| Volume | 46.5 km3[a] |
| Mass | (1.15±0.40)×1013 kg[6]: 3 |
Meandensity | 0.251±0.075 g/cm3[6]: 3 |
| 0.011–0.016 mm/s2[6]: 3 | |
| 0.0007 km/s at longest axis to 0.0009 km/s at poles | |
| synchronous | |
| zero | |
Pallene/pəˈliːniː/ is a very smallnatural satellite of Saturn. It is one of three small moons known as theAlkyonides that lie between the orbits of the largerMimas andEnceladus. It is also designatedSaturn XXXIII.
Pallene was discovered by the Cassini Imaging Team in 2004, during theCassini–Huygens mission.[7][8] It was given the temporary designationS/2004 S 2. In 2005, the name Pallene was provisionally approved by the IAU Division III Working Group for Planetary System Nomenclature,[9] and was ratified at the IAU General Assembly in 2006. The name refers toPallene, one of theAlkyonides, the seven beautiful daughters of thegiantAlkyoneus.
After the discovery in 2004, it was realized that Pallene had been first photographed on August 23, 1981, by the space probeVoyager 2. It had appeared in a single photograph and had been provisionally namedS/1981 S 14 and estimated to orbit 200,000 km from Saturn.[10] Because it had not been visible in other images, it had not been possible to compute its orbit at the time, but more recent comparisons showed it to match Pallene's orbit.[4]
Pallene is visibly affected by a perturbations from the much largerEnceladus, although this effect is not as large asMimas' perturbations onMethone. The perturbations cause Pallene'sosculating orbital elements to vary with an amplitude of about 4 km in semi-major axis, and 0.02° in longitude (corresponding to about 75 km). Eccentricity also changes on various timescales between 0.002 and 0.006, and inclination between about 0.178° and 0.184°.[4] It was previously thought that it was trapped in a 19:16orbital resonance with Enceladus,[4] but it is now known to be very close to but not actually in resonance.[11]
In 2006, images taken in forward-scattered light by theCassini spacecraft enabled the Cassini Imaging Team to discover a faint dust ring around Saturn that shares Pallene's orbit, now named thePallene Ring.[12][13] The ring has a radial extent of about 2,500 km. Its source is particles blasted off Pallene's surface by meteoroid impacts, which then form a diffuse ring around its orbital path.[14][15] Unlike the other Alkyonides andAegaeon, Pallene has no associated arc structure with it. Because the other moons are in orbital resonances and Pallene is not, ejecta from their surfaces remains locked in the same resonance as the moon is, and so shape into an arc instead of a complete ring.[11]
TheCassini spacecraft, which studied Saturn and its moons until September, 2017, performed a fly-by of Pallene on 16 October 2010, and 14 September 2011 at a distance of 36,000 kilometers (22,000 miles) and 44,000 kilometers respectively.[16]
Media related toPallene at Wikimedia CommonsListed in approximate increasing distance from Saturn | |||||||||
| Inner ring moons | |||||||||
| Co-orbitals | |||||||||
| Ring-embedded moons | |||||||||
| Major moons (withtrojans) | |||||||||
| Inuit group (36) |
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| Gallic group (17) | |||||||||
| Norse group (197) |
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| See also | |||||||||
| Geography | |
|---|---|
| Moons | |
| Astronomy | |
| Exploration | |
| Related | |
