Pallene (moon)

Pallene /pəˈliːniː/ is a very small natural satellite of Saturn. It is one of three small moons known as the Alkyonides that lie between the orbits of the larger Mimas and Enceladus. It is also designated Saturn XXXIII.

Pallene
Pallene in October 2010
Discovery
Discovered byVoyager 2 (first discovery)
Cassini Imaging Team[1]
Discovery dateJune 1, 2004 (second discovery by Cassini-Huygens)
Designations
Designation
Saturn XXXIII
Pronunciation/pəˈliːniː/[2]
Named after
Παλλήνη Pallēnē
S/1981 S 14 (first discovery)
S/2004 S 2 (second discovery)
AdjectivesPallenean /pælɪˈniːən/[3]
Orbital characteristics [4]
Epoch 20 June 2004 (JD 2453177.5)
212,280 ± 5 km
Eccentricity0.0040
1.153745829 d [5]
Inclination0.1810 ± 0.0014° (to Saturn's equator)
Satellite ofSaturn
GroupAlkyonides
Physical characteristics
Dimensions5.76 × 4.16 × 3.68±0.14[6]
Mean radius
2.22±0.07 km[6]
Mean density
0.25+0.09
−0.06 g/cm3[6]
synchronous
zero

    Discovery
    Discovery image of Pallene in 2004 from the Cassini probe

    Pallene was discovered by the Cassini Imaging Team in 2004, during the Cassini–Huygens mission.[7][8] It was given the temporary designation S/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 to Pallene, one of the Alkyonides, the seven beautiful daughters of the giant Alkyoneus.

    After the discovery in 2004, it was realized that Pallene had been first photographed on August 23, 1981, by the space probe Voyager 2. It had appeared in a single photograph and had been provisionally named S/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 recent comparisons have shown it to match Pallene's orbit.[4]

    Orbital characteristics

    Pallene is visibly affected by a perturbing mean-longitude resonance with the much larger Enceladus, although this effect is not as large as Mimas's perturbations on Methone. The perturbations cause Pallene's osculating 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]

    Ring

    In 2006, images taken in forward-scattered light by the Cassini spacecraft enabled the Cassini Imaging Team to discover a faint dust ring around Saturn that shares Pallene's orbit, now named the Pallene Ring.[11][12] 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.[13][14]

    Exploration

    The Cassini 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.

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    References
    1. Cassini Imaging Team.
    2. Noah Webster (1884) A Practical Dictionary of the English Language
    3. "JPL (ca. 2008) Cassini Equinox Mission: Pallene". Archived from the original on 2016-04-12. Retrieved 2020-03-05.
    4. Spitale Jacobson et al. 2006.
    5. NASA Celestia Archived March 9, 2005, at the Wayback Machine
    6. Thomas 2013.
    7. IAUC 8389.
    8. Porco Baker et al. 2005.
    9. IAUC 8471.
    10. IAUC 6162.
    11. IAUC 8759.
    12. CICLOPS 2006, Moonmade Rings.
    13. JPL/NASA: Creating New Rings.
    14. Hedman et al., 2009.

    Further reading
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