Tarvos (moon)

Tarvos /ˈtɑːrvɒs/, or Saturn XXI, is a prograde irregular satellite of Saturn. It was discovered by John J. Kavelaars et al. on September 23, 2000, and given the temporary designation S/2000 S 4. The name, given in August 2003, is after Tarvos, a deity depicted as a bull god carrying three cranes alongside its back from Gaulish mythology.^[8]

Tarvos

Animation of discovery images taken by the CFHT in September 2000
Discovery[1]
Discovered by	B. J. Gladman et al.[2]
Discovery date	September 23, 2000
Designations
Designation	Saturn XXI
Pronunciation	/ˈtɑːrvɒs/
Named after	Tarvos Trigaranus
Alternative names	S/2000 S 4
Adjectives	Tarvian[3]
Orbital characteristics[4]
Epoch 2000 January 1.5
Semi-major axis	18.215 Gm
Eccentricity	0.528
Orbital period (sidereal)	926.4 d (2.54 yr)
Inclination	38.6°
Satellite of	Saturn
Group	Gallic group
Physical characteristics
Mean diameter	15+50% −30% km[5]
Albedo	0.06 assumed[5]
Spectral type	light red B−V=0.77, R−V=0.57[6]
Apparent magnitude	22.1[7]
Absolute magnitude (H)	12.9[7]

Orbit

Discovery images of Tarvos (circled) taken by the CFHT

Tarvos orbits Saturn at an average distance of 18 million km in 926 days and is about 15 km in diameter (assuming an albedo of 0.06).^[5] It has a high orbital eccentricity of 0.53.^[4]

It is a member of the Gallic group of irregular satellites.

Origin

With a similar orbit and displaying a similar light-red colour to Albiorix, Tarvos is thought to have its origin in the break-up of a common progenitor^[6][9] or to be a fragment of that body.^[10]