Overview

Tarvos, also catalogued as Saturn XXI and S/2000 S 4, is a small irregular satellite of Saturn. It has a non-spherical shape and a light-red surface colour that links it to a family of similar outer moons. Its modest size and distant orbit place it among Saturn's many irregular satellites rather than the larger regular moons closer to the planet.

Physical characteristics

Tarvos is estimated to be roughly 15 kilometres in diameter, a value that depends on the assumed surface reflectivity (albedo ~0.04). The moon's irregular silhouette and spectral redness are typical of small, captured or fragmented bodies in the outer Saturnian system. Observations of its brightness and colour help classify it within a group of related satellites.

Orbit and group

Tarvos orbits Saturn at an average distance near 18 million kilometres and completes one orbit in about 926 days. It is a member of the Gallic group of prograde, irregular moons that share similar orbital distances and inclinations. The orbital and colour similarities are often cited when discussing the group's common origin. For more on its non-spherical nature see physical form and for orbital data consult discovery summaries such as discovery announcement and follow-up observations at satellite catalogs.

Discovery and name

Tarvos was discovered by John J. Kavelaars and collaborators on 23 September 2000 and initially received the provisional designation S/2000 S 4. The International Astronomical Union assigned the permanent name Tarvos in August 2003, drawing from Gaulish mythology. The naming process and official citation are discussed in notices and circulars about Saturn's satellites; see notices at naming bulletin.

Origin and significance

Because Tarvos shares orbit parameters and a similar light-red spectral signature with other Gallic moons, researchers propose it may be a fragment from a larger progenitor, possibly the larger Gallic moon Albiorix. This collisional-fragment hypothesis explains clusters of small bodies with matching colours and orbits. For comparative studies see materials on Albiorix and the Gallic group at Albiorix comparisons and overview resources at Gallic group summaries.

Notable facts

  • Designation: S/2000 S 4; permanent name Tarvos.
  • Estimated diameter: ~15 km (assuming low albedo).
  • Orbital period: ~926 days; semi-major distance: ~18 million km.
  • Belongs to the Gallic group of prograde irregular satellites.

Tarvos is a representative example of the small, dynamically interesting moons that populate the outer regions of the Saturn system and that offer clues to collisional and capture processes shaping satellite families. For further reading and data sets, consult dedicated mission archives and satellite catalogs linked above.