Skathi 



The moon of Saturn – Skathi (XXVII) – was previously temporarily designated as S/2000 S8. It was discovered in September 2000 by B. Gladman and J.J. Kavelaars. This discovery was achieved by the 3.6-m Canada-France-Hawaii telescope atop Mauna Kea (Hawaii). You can read additional details in The International Astronomical Union Circular (→IAU).
    Skathi is one of three new satellites discovered since the →Voyager-2 Saturn system fly-by which occured 19 years ago (1981). With this moon, the team discovered also: Thrymr and Mundilfari.
    Unlike moons discovered previously, the name does not come from Greek or Roman mythology. Skathi was a giantess in Scandinavian mythology.
    The moon by this name is in elliptical prograde orbit (→eccentricity e = 0.2698) with a →semimajor axis a = 15,540,000 km. At pericenter (closest to the planet) Skathi is separated from the Saturn a distance of q = 11,347,308 km. At apocenter (furthest from the planet) this moon is separated from the Saturn a distance of Q = 19,732,692 km. In future these parameters may vary due to a large orbital distance from Saturn and the orbital motion being disturbed by the Sun and other factors. Perhaps it is a captured asteroid (with a very diminutive mass: ~3.1472×1014 kg – it equals over 23 times less than a mountain like Giewont!), and in future will possibly return to heliocentric orbit.

    The orbital period is almost 2 earthly years, which means that the average speed of its celestial motion is only 0°29'40'' per day. When this motion was detected and compared to the changes in Saturn's position, this body was classified as a true planetary satellite (and not a distant celestial body with its position projected near the planet).
    Other obstacle in detecting this moon earlier was its brightness of only 23.6m (almost 11 million times fainter than the faintest stars visible to naked eye). For comparison: Saturn's brightness is about 0.7m, so Skathi is shining fainter by about 22.9m. The corresponding difference in brightness is almost 1.5 billion times!

I have given some crucial data of Skathi below. Table one contains the basic information. Whereas table two gives more detailed parametrs of its orbit (calculated using the following formulae).

Translated by Karol Pankowski


Skathi

Mean distance from the planet  [×103 km] 15,540.0
Mean distance from the planet  [planetary R] 257.8
Orbital period  [days] 728.20
Orbital eccentricity  [e] 0.2698
Orbit inclination  [degrees] 152.6
Mean diameter  [km] 8.0
Main discoverer and year of the discovery J.J. Kavelaars   2000
Visual magnitude  [mag] 23.6
Mass  [kg] ~3.1472 × 1014

Orbital Parameters

Pericenter
[q]
Apocenter
[Q]
Distance from the planet  [×103 km] 11,347.3 19,732.7
Distance from the planet  [planetary R] 188.3 327.4
Angular size of the moon's orbit observed from the Earth*  [degrees] 0°30'32.27'' 0°53'06.36''
Angular diameter of the planet's disc as observed from the moon  [degrees] 0°36'31.04'' 0°20'59.96''
Brightness of the planet as observed from the moon**  [mag] –9.6 –8.4
Diameter of the moon's disc as observed from the planet's "surface"  [degrees] 0°00'00.15'' 0°00'00.08''
Brightness of the moon as observed from the planet's "surface"**  [mag] 13.3 14.5
Orbital velocity  [km/sec] 2.06 1.18
  * This value is calculated for Saturn at opposition (distance 1.3 billion km = 8.5 AU)
** The given value of magnitude is not corrected for some decreasing factors (e.g. the changing phase of illumination)

See other related links:
Monde des MonatsSKATHI
THE SATURNIAN IRREGULARS HOME PAGE

The Astronomy Workshop – Satellite Viewer
Planetary Satellite Mean Orbital Parameters

Natural Satellite Physical Parameters



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