The moon of Jupiter – Euporie (XXXIV) – was previously temporarily designated as S/2001 J10. It was discovered in mid-December 2001 by the following team of astronomers: S.S. Sheppard, D.C. Jewitt and J. Kleyna. This discovery was achieved by the 3.6-m Canada-France-Hawaii telescope atop Mauna Kea (Hawaii). You can read additional details in Minor Planet Electronic Circular (MPEC).
    Euporie is one of eleven new satellites discovered since the →Voyager-2 Jupiter system fly-by which occured 22 years ago (1979). With this moon, the team discovered also: Autonoe, Thyone, Hermippe, Eurydome, Sponde, Pasithee, Euanthe, Kale, Orthosie and Aitne.
    The name of that moon is of mythological origin. Euporie was one of the Horai, daughters of Zeus and Themis (his second wife). Horai (gr. Hórai) were originally the impersonation of nature and they were depicted as beatiful maidens holding in their hand blossoms and fruit. Then they tended to become deities of ethical character and finally presided over the cycles of time: seasons and hours.
    The moon by this name is in elliptical retrograde orbit (→eccentricity e = 0.1432) with a →semimajor axis a = 19,304,000 km. At pericenter (closest to the planet) Euporie is separated from the Jupiter a distance of q = 16,539,667 km. At apocenter (furthest from the planet) this moon is separated from the Jupiter a distance of Q = 22,068,333 km. In future these parameters may vary due to a large orbital distance from Jupiter and the orbital motion being disturbed by the Sun and other factors. Perhaps it is a captured asteroid (with a microscopic mass: ~1.4987×1013 kg – it equals 490 times less than a mountain like Giewont!), and in future will possibly return to heliocentric orbit.

    The orbital period is about 1.5 earthly years, which means that the average speed of its celestial motion is only 0°39'13'' per day. When this motion was detected and compared to the changes in Jupiter'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 23.1m (over 6.9 million times fainter than the faintest stars visible to naked eye). For comparison: Jupiter's brightness is about –2.7m, so Euporie is shining fainter by about 25.8m. The corresponding difference in brightness is almost 21 billion times!

I have given some crucial data of Euporie 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


Mean distance from the planet  [×103 km] 19,304.0
Mean distance from the planet  [planetary R] 270.0
Orbital period  [days] 550.74
Orbital eccentricity  [e] 0.1432
Orbit inclination  [degrees] 145.8
Mean diameter  [km] 2.0
Main discoverer and year of the discovery S.S. Sheppard   2001
Visual magnitude  [mag] 23.1
Mass  [kg] ~1.4987 × 1013

Orbital Parameters

Distance from the planet  [×103 km] 16,539.7 22,068.3
Distance from the planet  [planetary R] 231.3 308.7
Angular size of the moon's orbit observed from the Earth*  [degrees] 1°30'26.47'' 2°00'41.01''
Angular diameter of the planet's disc as observed from the moon  [degrees] 0°29'43.15'' 0°22'16.42''
Brightness of the planet as observed from the moon**  [mag] –10.6 –10.0
Diameter of the moon's disc as observed from the planet's "surface"  [degrees] 0°00'00.03'' 0°00'00.02''
Brightness of the moon as observed from the planet's "surface"**  [mag] 15.2 15.8
Orbital velocity  [km/sec] 2.96 2.22
  * This value is calculated for Jupiter at opposition (distance 628.8 million km = 4.2 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 MonatsANANKEGRUPPE
Jupiter's 2002 Satellites

The Astronomy Workshop – Satellite Viewer
Planetary Satellite Mean Orbital Parameters
Natural Satellite Physical Parameters

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