Calypso is amoon ofSaturn. It was discovered in 1980, from ground-based observations, by Dan Pascu, P. Kenneth Seidelmann,William A. Baum, and Douglas G. Currie, and wasprovisionally designatedS/1980 S 25 (the 25th satellite of Saturn discovered in 1980).[7] Several other apparitions of it were recorded in the following months:S/1980 S 29,S/1980 S 30,[8]S/1980 S 32,[9] andS/1981 S 2.[10] In 1983 it was officially named afterCalypso ofGreek mythology.[c] It is also designatedSaturn XIV orTethys C.
Calypso is co-orbital with the moonTethys, and resides in Tethys's trailingLagrangian point (L5), 60 degrees behind Tethys. This relationship was first identified bySeidelmannet al. in 1981.[11] The moonTelesto resides in the other (leading) Lagrangian point of Tethys, 60 degrees in the other direction from Tethys. Calypso and Telesto have been termed "Tethys trojans", by analogy to thetrojan asteroids, and are half of the four presently knowntrojan moons.
Like many other small Saturnian moons and smallasteroids, Calypso is irregularly shaped, has overlapping large craters, and appears to also have loose surface material capable of smoothing the craters' appearance. Its surface is one of the most reflective (at visual wavelengths) in the Solar System, with a visualgeometric albedo of 1.34.[6] This very high albedo is the result of the sandblasting of particles fromSaturn's E-ring, a faint ring composed of small, water-ice particles generated byEnceladus's south polar geysers.[12]
^Calculated from Calypso's volume-equivalent sphere radius of9.5±0.4 km given by Thomas et al. (2020)[5]: 2
^Calculated by multiplying Calypso's volume with its assumed density of500 kg/m3.
^ Transactions of the International Astronomical Union, Vol. XVIIIA, 1982 (confirms Janus, names Epimetheus, Telesto, Calypso) (mentioned inIAUC 3872:Satellites of Jupiter and Saturn, September 30, 1983)
Seidelmann, P. K.; Harrington, R. S.; Pascu, D.; Baum, W. A.; Currie, D. G.; Westphal, J. A.; Danielson, G. E. (1981). "Saturn satellite observations and orbits from the 1980 ring plane crossing".Icarus.47 (2): 282.Bibcode:1981Icar...47..282S.doi:10.1016/0019-1035(81)90172-X.
