Telesto (Saturn Moon)

Telesto is a small Trojan moon of the sixth planet from the sun, Saturn. Telesto, which was discovered in 1980 by Smith, Reitsema, Larson and Fountain, is one of around 200 natural satellites in Saturnian orbit. It is one of only 62 moons that have a secure orbit, and only one of 53 named moons orbiting the ringed planet.

Telesto was officially designated S/1980 S 13 and was officially named in 1983 after the Greek sea goddess of the same name. This moon is also designated as Saturn XIII or Tethys B.

Telesto is co-orbital with Tethys, residing within that moon’s leading Lagrangian point. Lagrangian points are five positions in an orbital configuration where a small object (such as Telesto) affected only by gravity can theoretically be part of a constant-shape pattern with two larger objects. The Lagrangian points “mark positions where the combined gravitational pull of two large masses provides precisely the centripetal force required to orbit with them.”

The Telesto/Tethys relationship was first identified by Seidelmann et al. in 1981. Another moon, Calypso, resides in the other trailing Lagrangian point of Tethys. Telesto and Calypso are known as Trojan moons, as they are both moons of the Tethys moon that orbits Saturn. Saturn has two other Trojan moons in its system, hosted by the moon Dione.

On October 11, 2005, the NASA/ESA/ASI jointly-operated Cassini probe performed a distant flyby of Telesto. Images captured by Cassini show a surprisingly smooth surface, devoid of impact craters.


Orbital radius: 294,619 km
Diameter: 29 km (34 x 28 x 36)
Mass: Unknown
Orbital inclination: 1.19° (to Saturn’s equator)
Orbital period: 1.8878 days

Image Caption: Telesto as seen by the Cassini satellite on October 11, 2005. Credit: NASA/Wikipedia