Calypso (moon)

Dan Pascu, P. Kenneth Seidelmann, William A. tree, Douglas G. Currie

Calypso (or Saturn XIV) is the seventeenth and one of the smaller of the 62 known moons of the planet Saturn, as well as one of two Trojan moons of Tethys.

  • 3.1 size
  • 3.2 Internal structure
  • 3.3 Surface

Discovery and designation

Calypso was Kenneth Seidelmann, William discovered on the basis of ground-based telescopic observations on August 13, 1980 by the astronomer Dan Pascu, P. A. Tree and Douglas G. Currie; the moon first received the provisional designation S/1980 S 25 In the following months, Calypso received other designations S/1980 S 29 S/1980 S 30 S/1980 S 32, and S/1981 S 2, but all of which turned out to be the same object.

In 1983, she was officially named after Calypso, a nymph in Greek mythology, the seven years held the hero Odysseus on her island Ogygia. Odysseus was at the command of Zeus, transmitted by the messenger god Hermes, released. Ungern obeying, they supplied him with tools to build a raft, and later also with travel fare. Calypso is to be a daughter of the Titan Atlas.

The name in translation means mutatis mutandis, "hidden" " hiders ". Calypso is sometimes referred to as Tethys C.

Web properties


Calypso orbits Saturn on a prograde, nearly perfectly circular orbit at an average distance of 294,619 kilometers (about 4,888 Saturn radii ) from the center (or the center of gravity ), or about 234,351 km on whose cloud tops. The orbital eccentricity is 0.0005, the orbit is inclined 1.56 ° relative to the equator of Saturn, that is nearly in the equatorial plane of the planet. Due to the very low eccentricity, the web varies in distance to Saturn at about 295 km.

The orbits of the next inner moon Enceladus is removed an average of about 56,671 km from the orbit of Calypso, the distances of the orbits of the moons Dione and their next outer Trojan moons Helene and Polydeuces are on average about 82,777 km.

Calypso orbits Saturn in 1 day, 21 hours, 18 minutes and 26.1 seconds. This is about 2 hours and 50.9 minutes longer than the orbital period of Jupiter's moon Io. Calypso required for one revolution about 12 hours, and 25.3 minutes longer than the inner adjacent Enceladus.

The Orbit of Calypso lies deep in the magnetosphere of Saturn, so that the plasma co-rotates with the planet that meets the following hemisphere. It is thus also hit by energetic particles (electrons and ions).

Train resonances

The orbit of Calypso is co-orbital with the orbits of the much larger, dominant Tethys and the slightly larger Telesto. These so-called Tethys Trojan moons, Telesto and Calypso, run in Tethys ' Lagrange points L4 and L5, respectively at an angular distance of 60 ° in front and behind the moon, on the same orbit around the planet ( 1:1 orbital resonance ). Calypso runs it through the following Lagrangian point L5, and therefore brings up the rear of the shared orbit. Telesto leads them in the leading Lagrange point L4, 60 ° behind follows Tethys, another 60 ° behind it finally follows Calypso.

Tethys and its two Trojan moons orbit Saturn within the E ring, so that the surfaces of the moons are in a constant bombardment by micrometeorites.


The rotation period is equal to the orbital period and Calypso has with how the Earth's moon and all the major satellites of the gas giant, in a synchronous rotation, which thus also takes place within 1 day 21 hours, 18 minutes and 26.1 seconds, so always shows with the same hemisphere to Saturn. The axis of rotation is inclined 0 ° to the orbit, so is therefore precisely perpendicular to the plane of rotation.

Physical Properties


Calypso is irregularly shaped, with a mean diameter of 21.4 km. The exact dimensions are 30.2 × 23.0 × 14.0 km, which gives the moon the shape of a triaxial ellipsoid. The longitudinal axis is aligned with Saturn, the central axis is between leading and following hemisphere and the shortest axis between the poles. Calypso is the nine- tenth-largest moon of Saturn.

From the size Calypso is to be compared approximately with the larger Martian moon Phobos.

The total area of ​​1439 km ² Telesto is about, this is about the middle of the faces of the Swiss cantons of Lucerne and Aargau.

Internal construction

The density is 0.5 g/cm3 with very low, which suggests that Calypso is composed mainly of water ice. The low density indicates that it may be one of the so-called Rubble Piles, which, due to the relatively weak gravitational inside cavities.


The Trabant has a very bright surface with an albedo of 0.70, ie, 70 % of the incident sunlight is reflected. Clearly visible are several impact craters from meteorites. Generally, however, the surface is very smooth and has few traces of older craters, indicating a thick layer of fine-grained ice - regolith, possibly resulting from the continuous bombardment by the particles of the E- ring.


From the Earth as seen from Saturn companion with an apparent brightness of 18.7 m ( 1:15900000 of the central planet is ), a light faint object.

Calypso was attended by current four spacecraft, notably by the flyby probes Voyager 1 on 12 November 1980 and Voyager 2 on August 25, 1981, Cassini -Huygens, the orbiting Saturn since July 1, 2004. The last flyby by Cassini took place on 13 February 2010, when the probe Calypso happened at a distance of 23,000 km.