S/2004 S 13

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S/2004 S 13 is ∼4 kilometers in size and thus among the smallest known irregular moons of Saturn. It has been discovered in 2004 joint with eleven other outer Saturnian moons. Its mean distance to Saturn is ∼18½ million kilometers, with one revolution around the planet on a retrograde orbit lasting approximately 2 years, 6 months and 3 weeks.

This moon is effectively lost and requires a re-discovery because its orbital elements are not known at sufficient precision for easy recovery. It has not been named yet. We made no attempt to observe it with Cassini because the position was not known.

Table of contents

(1) Astronomical and physical properties

This page is intended to compile (much of) our knowledge of unnamed moon S/2004 S 13 in compact form, including general information like discovery circumstances and orbital and physical parameters. For further reading on irregular moons of Saturn in general, see the reference list at my outer-Saturnian moons page.

Last update: 28 Apr 2022 — page content is best displayed on a screen at least 1024 pixels wide

(1) Astronomical and physical properties

Moon name Saturn range Orbit period Orbit direction Size Rotation period Discovery year
S/2004 S 13
million km

Basic information about S/2004 S 13 is offered in tabular form:
(1A) Basic properties
← Table (Basic properties) in text format [ not available yet ]

Most fundamental values are highlighted in red. The notes offer explanations, calculations, accuracies, references, etc. The data were obtained from ground-based observations.

(1A) Basic properties
Moon name(1) Orbit direction(6) retrograde Mean size(8) 4 km
Provisional name(2) S/2004 S 13 Semi-major axis(7) 18.4 ⋅ 106 km First observation date(9) 12 Dec 2004
Moon abbrev. (TD)(3) 4S13 Orbit eccentricity(7) 0.26 Announcement date(9) 04 May 2005
Group member(4) Norse Orbit inclination(7) 169° IAU circ. announcement(9) no. 8523
Dynamical family(5) Mundilfari Orbital period(7) 936 d Discoverers(10) S. Sheppard et al.

Table notes:

(1) The object has no proper name yet.

(2) Designation given to the object in the first announcement; the guidelines are explained here.

(3) I use this 4-letter abbreviation in the diagrams of my publications simply for practicability reasons. It has no offcial character.

(4) Norse, Inuit, or Gallic.

(5) Classification based on the a,e,i space in Fig. 1 and Table 2 in Denk et al. (2018). Note that at this point, a collisional relation between the two objects remains speculative.

(6) Prograde (counterclockwise as seen from north) or retrograde (clockwise as seen from north).

(7) Orbit semi-major axis a, orbit eccentricity e, orbit inclination i, orbit period P are from JPL’s Solar System Dynamics Planetary Satellite Mean Elements website.

(8) Object diameter guess based on the measured brightness; from Table 2 in Denk et al. (2018). The true size may well be off by ±50%.

(9) The date of the photography wherein the object was spotted for the first time is given in the IAU circular released on the announcement date.

(10) The discoverer team included: Scott Sheppard, David Jewitt, and Jan Kleyna.

© Tilmann Denk (2022)