Irregular moons of Saturn -- Tarvos For notes, see https://tilmanndenk.de/outersaturnianmoons/tarvos/#1 22 Oct 2018 / TD Overview Table Moon name Tarvos Saturn range 18e6 km Orbit period 2.5 years Orbit direction prograde Size ~ 15 km Rotation period 10 41 hh:mm Discovery year 2000 (A) Designations and discovery circumstances (A1) Moon name Tarvos (A2) Moon abbrev. (TD) Tar (A3) IAU number Saturn XXI (A4) Provisional designation S/2000 S 4 (A5) SPICE ID 621 (A6) Also-used label S21 (A7) First observation date 23 Sep 2000 (A7) Announcement date 25 Oct 2000 (A7) IAU circular announcement no. 7513 (A8) Discoverers Kavelaars, Gladman, et al. (B) Orbit parameters (B1) Orbit direction prograde (B2) Group member Gallic (B3) Dynamical family Gallic (B4) Periapsis range 8.43e6 km (B5) Semi-major axis 18.24e6 km (B6) Apoapsis range 28.05e6 km (B7) Semi-major axis 302 R_Saturn (B8) Semi-major axis 0.122 au (B9) Semi-major axis 0.28 R_Hill (B10) Orbit eccentricity 0.54 (B11) Orbit inclination 33.7 ° (B12) Inclination supplemental angle 33.7 ° (B13) Orbital period 926 d (B14) Orbital period 2 6 1.75 y:m:w (B15) Mean orbit velocity 1.44 km/s (C) Physical parameters (C1) Mean size ~ 15 -3 +4 km (C2) Mean radius ~ 7.3 km (C3) Equatorial circumference ~ 50 km (C4) Minimum equatorial axes ratio 1.08 (C5) Axes radii (a x b x c) ~ unknown (C5) (C6) Mass ~ 8e14 kg (C7) Mean density (?) 0.5 g/cm^3 (C8) Surface escape velocity ~ 10 km/h (C9) Rotation period (sidereal) 10.691 h (C9) Rotation period error 0.001 h (C9) Spin rate 2.245 d^(-1) (C10) Spin direction unknown (C11) Seasons unknown (C12) Pole direction (ecliptic longitude λ) unknown (C12) Pole direction (ecliptic latitude β) unknown (C13) Pole direction (geocentric RA) unknown (C13) Pole direction (geocentric Dec) unknown (C14) Absolute visual magnitude ~ 12.9 mag (C15) Apparent visual magnitude from Earth 22.1 mag (C16) Best apparent magnitude for Cassini 12.8 mag (C17) Spectral slope ~ +5.4 %/100nm (C17) B-R color index ~ 1.21 1.13 (C18) Albedo (?) 0.06 (C19) Hill sphere radius ~ 650 km (C20) Hill sphere radius ~ 90 r_Tar