Farbauti (S/2004 S 9)

back to Outer Saturnian Moons

Farbauti is ∼4 kilometers in size and thus one of the small Irregular moons of Saturn. It has been discovered in 2004 joint with eleven other outer moons. Farbauti’s mean distance to Saturn is ∼20½ million kilometers, with one revolution around the planet on a retrograde orbit requiring almost exactly 3 years.

Since Farbauti’s ephemeris (position in the sky) is not accurately known, we never made an attempt to observe it with Cassini. During the second part of the mission (Cassini Solstice Mission), Farbauti was also too dark for the Cassini camera to obtain images useful for lightcurves.

This page is intended to compile (much of) our knowledge of Farbauti 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.

This website is still under development and will get additional content (like orbital and physical parameters) in the near future. I will remove this note when the page will be close to completion.

Last update: 20 May 2023 — 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
million km

Basic information about Farbauti 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) Farbauti Orbit direction(7) retrograde Mean size(11) ∼ 4 km
Moon abbrev.(2) Far Semi-major axis(8) 20.390 ⋅ 10km Absolute visual magnitude(12) ∼ 15.6 mag
IAU number(3) Orbit eccentricity(8) 0.241 Apparent vis. mag. from Earth(13) 24.7 mag
Provisional desig.(4) S/2004 S 9 Orbit inclination(8) 156.5° First observation date(14) 12 Dec 2004
SPICE ID(5) 640 Orbital period(8) 1087.8 d Announcement date(14) 04 May 2005
Also-used label(6) Group member(9) Norse IAU circ. announcement(14) no. 8523
Dynamical family(10) Bergelmir (?) Discoverers(15) S. Sheppard et al.

Table notes:

(1) The object has no proper name yet.

(2) I use this 3-letter abbreviation in the diagrams of my publications simply for practicability reasons. These have no offcial character.

(3) Moon numbers are assigned by the International Astronomical Union (IAU)’s Committee for Planetary System Nomenclature. For satellites, Roman numeral designations are used.

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

(5) SPICE is a commonly-used information system of NASA’s Navigation and Ancillary Information Facility (NAIF). It assists engineers in modeling, planning, and executing planetary-exploration missions, and supports observation interpretation for scientists. Each planet and moon obtained a unique SPICE number.

(6) ‘S’ for ‘Saturnian moon’ plus the roman numeral designation in arabic numbers are often-used labels for satellites. Not sure how official that is.

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

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

(9) Norse, Inuit, or Gallic.

(10) Classification based on the a,e,i space in Fig. 1 and Table 2 in Denk et al. (2018).

(11) Determined from absolute visual magnitude H (see note (12)). The conversion from H to size (diameter of a reference sphere) was calculated through $D=1 \text{ au}\cdot \frac{2}{\sqrt{A}}\cdot 10^{−0.2·(H−M_☉)}$; with solar apparent V magnitude M = −26.71 ± 0.02 mag and Astronomical Unit 1 au = 149 597 870.7 km. For the object’s albedo A, a value of 0.06 is assumed (see discussions in Grav et al. (2015) and Denk et al. (2018) on albedo uncertainties). Due to the uncertain input values, a size determined this way may be uncertain to ∼ −15/+30% (for A ± 0.02 and H ± 0.1).

(12) From MPEC; the number may be uncertain by several tenths of magnitude. The absolute visual magnitude HV is the magnitude (brightness) of an object (in the visible wavelength range) if located 1 au away from the sun and observed at 0° phase angle (i.e., in this definition, the observer virtually sits at the center of the sun). The magnitude scale is logarithmic, with an object of 6th mag being 100x darker than a 1st mag object.

(13) Apparent visual magnitude V; from S. Sheppard’s website.

(14) 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. 

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

© Tilmann Denk (2023)