Rhéa (the moon)

See also: Rhéa

|----- ! bgcolor=" black" colspan=" 2" |
Cliquez on the image for a description |----- ! bgcolor=" #6295da" colspan=" 2" | Discovered |----- | Discovered by | Jean-Dominique Cassini |----- | Discovered in || December 23rd 1672 |----- ! bgcolor=" #6295da" colspan=" 2" | Characteristics of the Orbit |----- | Equatorial radius || 527.100 km |----- | orbital Eccentricity || 0,0009 |----- | Period of revolution || 4,518 J |----- | Slope || 0,327° |----- | Natural satellite of || Saturn |----- ! bgcolor=" #a0ffa0" colspan=" 2" | Physical characteristics |----- | Diameter with the equator || 1528 km |----- | Mass || 2,32×10²¹ kg |----- | Density average || 1,24×10³ kg/m³ |----- | Gravity of surface || 0,26 m/s² |----- | Period of rotation || synchronous |----- | Albedo || 0,6 |----- | Temperature of surface | |----- | Atmosphere | no atmosphere |} Rhéa (S V Rhea) is the second the moon of Saturn by the size (after Titan). She was discovered in 1672 by Jean-Dominique Cassini alias Giovanni Domenico Cassini.

History

Cassini named the four moons which he discovered (Téthys, Dioné, Rhéa and Japet) Sidera Lodoicea (“stars of Louis”) in the honor of the king Louis XIV. Titan, discovered by Christiaan Huygens almost thirty years earlier, had simply baptized it Saturni Luna (“the Saturn moon”). Also the astronomers took the practice to call them Saturn 1 with Saturn 5 .

It is only in 1847 that Sir John Herschel, wire of William Herschel (discoverer of Mimas and Encélade in 1789), proposed that numerical designations are replaced by the names of Titans, brothers and sisters of Cronos (i.e Saturn). Rhéa was the woman of Cronos; tired of what this one devours his/her children, it made him swallow a rock in order to save her son Zeus.

The Rhéa satellite was flown over by Voyager 1 in November 1980 and on November 26th 2005 by the probe Cassini, which passed to close to 500km to the top of its surface.

Properties

Rhéa is a frozen body of weak density (1240 kg/m ³), which seems to indicate that the moon is made up of a rock core counting only for one third of the mass of Rhéa, the remainder being mainly of ice-cold water. The characteristics of Rhéa are similar to those of Dioné, with hemispheres before and back differentiated, which can suppose a similar composition and a history. The temperature on the surface of Rhéa is of -174 °C with the sun, and of -200°C with -220°C in the shade.

Rhéa is strongly cratérisée and its surface is traversed clear marks. This one can be divided into two geological zones differentiated by the density of the crater S: the first zone includes/understands craters of more than 40 km in diameter, whereas the second, partly in the polar regions and equatorial, is covered with craters of less than 40 km in diameter. That would indicate that a resulting major event in a patching took place during its formation.

The front hemisphere is strongly cratérisé and uniformly clearly. Like Callisto, the craters are deprived of the structures to the relief marked present on the the Moon and Mercure. The hemisphere postpones presents a network of clear trails on a dark bottom, and few craters. These trails could be ejected matter of Volcan S of ice whereas Rhéa was still liquid under surface.

Toponymy

The remarkable formations of the surface of the satellite were named according to loans with the various myths of the genesis of the world.

One finds as follows: Faro (divinity Sudan ease of water), Ormazd (Iran), Izanami and Izanagi (paramount couple Japan board), Qat (Mélanésie)…

See too

Saturn
the goddess Rhéa
the Asteroid (577) Rhéa

External bond

Rhéa, on the site SolarViews.com

Simple: Rhea (moon) Zh-classical: 土衛五