Rhea (moon)

Rhea
	Mosaic of Rhea, assembled from Cassini imagery taken on 26 November 2005
Discovery
Discovered by	G. D. Cassini
Discovery date	December 23, 1672
Designations
Designation	Saturn V
Pronunciation	/ˈriː.ə/
Named after	Ῥέᾱ Rheā
Adjectives	Rhean /ˈriː.ən/
Orbital characteristics
Semi-major axis	527040 km
Eccentricity	0.001
Orbital period (sidereal)	4.518212 d
Average orbital speed	8.48 km/s
Inclination	0.35°
Satellite of	Saturn
Physical characteristics
Dimensions	1532.4 × 1525.6 × 1524.4 km
Mean radius	763.5±0.5 km
Surface area	7325342 km2
Mass	(2.3064854±0.0000522)×1021 kg (~3.9×10−4 Earths)
Mean density	1.2372±0.0029 g/cm3
Surface gravity	0.26 m/s2
Moment of inertia factor	0.3911±0.0045 (disputed/unclear)
Escape velocity	0.635 km/s
Synodic rotation period	4.518212 d ; (synchronous)
Axial tilt	zero
Albedo	0.949±0.003 (geometric)
Apparent magnitude	10

Rhea (/ˈriː.ə/) is the second-largest moon of Saturn and the ninth-largest moon in the Solar System, with a surface area that is comparable to the area of Australia. It is the smallest body in the Solar System for which precise measurements have confirmed a shape consistent with hydrostatic equilibrium. Rhea has a nearly circular orbit around Saturn, but it is also tidally locked, like Saturn's other major moons; that is, it rotates with the same period it revolves (orbits), so one hemisphere always faces towards the planet.

The moon itself has a fairly low density, composed of roughly three-quarters ice and only one-quarter rock. The surface of Rhea is heavily cratered, with distinct leading and trailing hemispheres. Like the moon Dione, it has high-albedo ice cliffs that appear as bright wispy streaks visible from space. The surface temperature varies between −174 °C and −220 °C.

Rhea was discovered in 1672 by Giovanni Domenico Cassini. Since then, it has been visited by both Voyager probes and was the subject of close targeted flybys by the Cassini orbiter in 2005, 2007, 2010, 2011, and once more in 2013.

^ ^a ^b Tillman, Nola Taylor (2016-06-29). "Rhea: Saturn's dirty snowball moon". space.com.
^ Consulmagno, G.; Ryche, H. (Feb 9, 1982). "Pronouncing the names of the moons of Saturn" (PDF). EOS. 63 (6): 146–147. doi:10.1029/EO063i006p00146. Retrieved Nov 30, 2022.
^ Moore et al. (1984) "The Geomorphology of Rhea", Proceedings of the fifteenth Lunar and Planetary Science, Part 2, p C-791–C-794
^ Cite error: The named reference NSES was invoked but never defined (see the help page).
^ ^a ^b ^c Cite error: The named reference NSSDC was invoked but never defined (see the help page).
^ Cite error: The named reference Roatsch et al. 2009 was invoked but never defined (see the help page).
^ ^a ^b ^c Robert. A. Jacobson (18 October 2022). "The Orbits of the Main Saturnian Satellites, the Saturnian System Gravity Field, and the Orientation of Saturn's Pole". The Astronomical Journal. 164 (5). Bibcode:2022AJ....164..199J. doi:10.3847/1538-3881/AC90C9. ISSN 0004-6256. S2CID 252992162. Wikidata Q126389785.
^ Anderson, J. D.; Schubert, G. (2007). "Saturn's satellite Rhea is a homogeneous mix of rock and ice". Geophysical Research Letters. 34 (2): L02202. Bibcode:2007GeoRL..34.2202A. doi:10.1029/2006GL028100.
^ Cite error: The named reference Anderson2008 was invoked but never defined (see the help page).
^ Cite error: The named reference Verbiscer et al. 2007 was invoked but never defined (see the help page).
^ Cite error: The named reference Observatorio ARVAL was invoked but never defined (see the help page).

Cite error: There are <ref group=lower-alpha> tags or {{efn}} templates on this page, but the references will not show without a {{reflist|group=lower-alpha}} template or {{notelist}} template (see the help page).

[space.com.Rhea-1] Tillman, Nola Taylor (2016-06-29). "Rhea: Saturn's dirty snowball moon". space.com.

[2] Consulmagno, G.; Ryche, H. (Feb 9, 1982). "Pronouncing the names of the moons of Saturn" (PDF). EOS. 63 (6): 146–147. doi:10.1029/EO063i006p00146. Retrieved Nov 30, 2022.

[3] Moore et al. (1984) "The Geomorphology of Rhea", Proceedings of the fifteenth Lunar and Planetary Science, Part 2, p C-791–C-794

[NSES-4] Cite error: The named reference NSES was invoked but never defined (see the help page).

[NSSDC-5] Cite error: The named reference NSSDC was invoked but never defined (see the help page).

[Roatsch_et_al._2009-7] Cite error: The named reference Roatsch et al. 2009 was invoked but never defined (see the help page).

[Jacobson2022-8] Robert. A. Jacobson (18 October 2022). "The Orbits of the Main Saturnian Satellites, the Saturnian System Gravity Field, and the Orientation of Saturn's Pole". The Astronomical Journal. 164 (5). Bibcode:2022AJ....164..199J. doi:10.3847/1538-3881/AC90C9. ISSN 0004-6256. S2CID 252992162. Wikidata Q126389785.

[Anderson2007-11] Anderson, J. D.; Schubert, G. (2007). "Saturn's satellite Rhea is a homogeneous mix of rock and ice". Geophysical Research Letters. 34 (2): L02202. Bibcode:2007GeoRL..34.2202A. doi:10.1029/2006GL028100.

[Anderson2008-12] Cite error: The named reference Anderson2008 was invoked but never defined (see the help page).

[Verbiscer_et_al._2007-13] Cite error: The named reference Verbiscer et al. 2007 was invoked but never defined (see the help page).

[Observatorio_ARVAL-14] Cite error: The named reference Observatorio ARVAL was invoked but never defined (see the help page).

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