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Calypso is a
moon
The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width of ...
of
Saturn
Saturn is the sixth planet from the Sun and the second-largest in the Solar System, after Jupiter. It is a gas giant with an average radius of about nine and a half times that of Earth. It has only one-eighth the average density of Earth; h ...
. It was discovered in 1980, from ground-based observations, by Dan Pascu, P. Kenneth Seidelmann,
William A. Baum, and Douglas G. Currie, and was
provisionally designated (the 25th satellite of Saturn discovered in 1980). Several other apparitions of it were recorded in the following months: , , , and . In 1983 it was officially named after
Calypso of
Greek mythology
A major branch of classical mythology, Greek mythology is the body of myths originally told by the ancient Greeks, and a genre of Ancient Greek folklore. These stories concern the origin and nature of the world, the lives and activities o ...
. It is also designated or Tethys C.
Calypso is co-orbital with the moon
Tethys, and resides in Tethys' trailing
Lagrangian point
In celestial mechanics, the Lagrange points (; also Lagrangian points or libration points) are points of equilibrium for small-mass objects under the influence of two massive orbiting bodies. Mathematically, this involves the solution of t ...
(), 60 degrees behind Tethys. This relationship was first identified by
Seidelmann ''et al.'' in 1981. The moon
Telesto 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 the
trojan asteroid
In astronomy, a trojan is a small celestial body (mostly asteroids) that shares the orbit of a larger body, remaining in a stable orbit approximately 60° ahead of or behind the main body near one of its Lagrangian points and . Trojans can shar ...
s, and are half of the four presently known
trojan moon
In astronomy, a co-orbital configuration is a configuration of two or more astronomical objects (such as asteroids, moons, or planets) orbiting at the same, or very similar, distance from their primary, i.e. they are in a 1:1 mean-motion resonance ...
s.
Like many other small Saturnian moons and small
asteroid
An asteroid is a minor planet of the inner Solar System. Sizes and shapes of asteroids vary significantly, ranging from 1-meter rocks to a dwarf planet almost 1000 km in diameter; they are rocky, metallic or icy bodies with no atmosphere. ...
s, 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 visual
geometric albedo
In astronomy, the geometric albedo of a celestial body is the ratio of its actual brightness as seen from the light source (i.e. at zero phase angle) to that of an ''idealized'' flat, fully reflecting, diffusively scattering ( Lambertian) disk wi ...
of 1.34. This very high albedo is the result of the sandblasting of particles from
Saturn's E-ring, a faint ring composed of small, water-ice particles generated by
Enceladus
Enceladus is the sixth-largest moon of Saturn (19th largest in the Solar System). It is about in diameter, about a tenth of that of Saturn's largest moon, Titan. Enceladus is mostly covered by fresh, clean ice, making it one of the most refle ...
' south polar geysers.
Gallery
File:Calypso crop resize sharp.jpg, Another February 13, 2010 image showing flow-like albedo
Albedo (; ) is the measure of the diffuse reflection of solar radiation out of the total solar radiation and measured on a scale from 0, corresponding to a black body that absorbs all incident radiation, to 1, corresponding to a body that refle ...
features
File:Calypso image PIA07633.jpg, ''Cassini'' image from September 23, 2005
File:Calypso - Voyager 2.jpg, Calypso as seen by ''Voyager 2
''Voyager 2'' is a space probe launched by NASA on August 20, 1977, to study the outer planets and interstellar space beyond the Sun's heliosphere. As a part of the Voyager program, it was launched 16 days before its twin, '' Voyager 1'', ...
'' (August 1981)
See also
*
List of natural satellites
References
Notes
Citations
Sources
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* (supporting online material, table S1)
External links
Calypso Profileb
NASA's Solar System ExplorationAnimation of photos from Cassini 2010-02-13 flyby on YouTubeRaw images
{{DEFAULTSORT:Calypso (Moon)
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Moons of Saturn
Trojan moons
Calypso (mythology)
Moons with a prograde orbit