Galatea (moon)
Fourth-closest inner moon of Neptune, shepherd of the Adams ring.
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Galatea is a small, irregularly shaped moon of Neptune discovered in Voyager 2 images from late July 1989.[1][2] It likely formed as a rubble pile from fragments of Neptune's original satellites that were disrupted by Triton's capture.[3] Galatea functions as a shepherd moon for the ring located 1000 km beyond its orbit, the Adams ring, and its surface includes hydrated materials whose composition is similar to carbonaceous chondrites and main-belt asteroids like Ceres.[4][5]
Key facts and history
Galatea received the temporary designation S/1989 N 4 upon its discovery announcement on 2 August 1989.[1][2] The IAU Circular noted that Galatea's orbit appeared prograde, nearly circular, and equatorial, with suggestions of nonzero eccentricity or inclination.[2] Its surface has a deep 3-μm OH band and phyllosilicates, but lacks clear water ice signatures.[5] The presence of phyllosilicates indicates that Galatea's material was altered by water at temperatures between 300 and 400 K and never exceeded 700 K.[6]
The Voyager 2 probe's narrow-angle imaging data, consisting of ten frames taken over five days, led to the discovery of Galatea (temporarily designated 1989 N 4), with the announcement made on 2 August 1989, implying the discovery occurred before July 28.[1][2] On 16 September 1991, the IAU Executive Committee approved the name Galatea for the satellite previously known as 1989 N 4.[7][8] At wavelengths of 1.4 and 2.0 microns, Galatea's surface albedo measures 0.08; this value falls to 0.04 at 3.0 microns and climbs to 0.12 at 4.6 microns.[6]
What the cited sources add
The IAU Circular from 2 August 1989 states that Galatea was 2.5 to 3.0 magnitudes fainter than Neptune's moon 1989 N1 in Voyager 2's clear filter.[2] The same circular notes that preliminary calculations suggested Galatea's orbit might have nonzero eccentricity or inclination.[2] The 1991 IAU Circular confirms that the IAU Executive Committee approved the name Galatea for the satellite previously designated 1989 N4.[8]
References
- Wikipedia, "Galatea (moon)" (CC BY-SA 4.0), which cites: Marsden, "Satellites of Neptune", IAU Circular, August 2, 1989 (we also read that source) en.wikipedia.org
- Marsden, "Satellites of Neptune", IAU Circular, August 2, 1989. facts only, no text reused. cbat.eps.harvard.edu
- Wikipedia, "Galatea (moon)" (CC BY-SA 4.0), which cites: Banfield, "A dynamical history of the inner Neptunian satellites", Icarus, October 1992, p. 390–401 (original not read by us) en.wikipedia.org
- Wikipedia, "Galatea (moon)" (CC BY-SA 4.0), which cites: Namouni, "The confinement of Neptune's ring arcs by the moon Galatea", Nature, 2002, p. 45–7; Madeira, "Numerical analysis of processes for the formation of moonlets confining the arcs of Neptune", Monthly Notices of the Royal Astronomical Society, 2022-04-21, p. 297–309; Porco, "An Explanation for Neptune's Ring Arcs", Science, 1991, p. 995–1001 (original not read by us) en.wikipedia.org
- Wikipedia, "Galatea (moon)" (CC BY-SA 4.0), which cites: Belyakov, "JWST Spectrophotometry of the Small Satellites of Uranus and Neptune", The Planetary Science Journal, 2024-05-01, p. 119 (original not read by us) en.wikipedia.org
- Wikipedia, "Galatea (moon)" (CC BY-SA 4.0), which cites: Davis, "Neptune's inner moons and rings are exposed icy body interiors", Science Advances, 2026; Belyakov, "JWST Spectrophotometry of the Small Satellites of Uranus and Neptune", The Planetary Science Journal, 2024-05-01, p. 119 (original not read by us) en.wikipedia.org
- Wikipedia, "Galatea (moon)" (CC BY-SA 4.0), which cites: Marsden, "Satellites of Saturn and Neptune", IAU Circular, September 16, 1991 (we also read that source) en.wikipedia.org
- Marsden, "Satellites of Saturn and Neptune", IAU Circular, September 16, 1991. facts only, no text reused. cbat.eps.harvard.edu
Each numbered sentence above was checked against the source it cites before publication. Sentences citing Wikipedia adapt text from the English Wikipedia article Galatea (moon) (contributors), used under CC BY-SA 4.0; this entry is available under the same licence. Other sources were used for facts only; no text or images are copied from them.
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Sources
Compiled from Wikipedia and the sources listed below. Text from Wikipedia is available under CC BY-SA 4.0; this entry is adapted from it.
- Wikipedia: Galatea (moon) (CC BY-SA 4.0).
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