The moon of Jupiter – S/2003 J2 – was discovered in
February 2003 by S.S. Sheppard
.
This discovery was achieved by 8.3-m Subaru telescope
atop Mauna Kea (Hawaii). You can read additional details in The International Astronomical Union Circular
(→IAU).
S/2003 J2 is one of seven new satellites new satellites discovered since
the →Voyager-2
Jupiter system fly-by which occured 24 years ago (1979). With this moon, the astronomer discovered also: Eukelade, S/2003
J3, S/2003 J4, S/2003
J5, Helike and Aoede.
The moon is in elliptical retrograde orbit (→eccentricity
e = 0.4074) with a →semimajor axis a = 28,455,000 km. At pericenter (closest to the planet) S/2003 J2 is separated from the Jupiter a distance of q = 16,862,433 km. At apocenter (furthest from the planet) this moon is separated from the Jupiter a distance of Q = 40,047,567 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.
An interesting feature of that moon is that it is currently believed to be the outermost moon of Jupiter!
The orbital period is almost 2.7 earthly years, which means that the average speed of its celestial motion is
only 0°22'00'' 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 23.2m
(almost 7.6 million times fainter than the faintest stars visible to naked eye). For comparison: Jupiter's brightness is about
–2.7m,
so S/2003 J2 is shining fainter by about 25.9m.
The corresponding difference in brightness is almost 23 billion times!
I have given some crucial data of S/2003 J2 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
– 
