The Moons of the Solar System

Carpo

The moon of Jupiter – Carpo (XLVI) – was previously temporarily designated as S/2003 J20. It was discovered in April 2003 by B. Gladman. 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).
    Carpo is one of two 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 S/2003 J19.
    The moon is in elliptical prograde orbit (→eccentricity e = 0.4316) with a →semimajor axis a = 17,058,000 km. At pericenter (closest to the planet) Carpo is separated from the Jupiter a distance of q = 9,695,767 km. At apocenter (furthest from the planet) this moon is separated from the Jupiter a distance of Q = 24,420,233 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: ~4.4960×10¹³ kg – it equals 163 times less than a mountain like Giewont!), and in future will possibly return to heliocentric orbit.

    An in teresting feature of that moon is that being the in nermost ''irregular'' satellite of Jupiter (in a higly inclined elliptical orbit), it revolves in the same direction as the planet is spinning on its axis. Due to its similarity in semimajor axis to some of the other satellites of Jupiter,

    The orbital period is over 1.25 earthly years, which means that the average speed of its celestial motion is only 0°47'20'' 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 23.0^m (over 6.3 million times fainter than the faintest stars visible to naked eye). For comparison: Jupiter's brightness is about –2.7^m, so Carpo is shining fainter by about 25.7^m. The corresponding difference in brightness is over 19 billion times!

I have given some crucial data of Carpo 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

Carpo
Mean distance from the planet  [×10³ km] 17,058.0
Mean distance from the planet  [planetary R] 238.6
Orbital period  [days] 456.30
Orbital eccentricity  [e] 0.4316
Orbit inclination  [degrees] 51.6
Mean diameter  [km] 3.0
Main discoverer and year of the discovery S.S. Sheppard   2003
Visual magnitude  [mag] 23.0
Mass  [kg] ~4.4960 × 10¹³

Orbital Parameters
Pericenter
[q] Apocenter
[Q]

Distance from the planet  [×10³ km] 9,695.8 24,420.2
Distance from the planet  [planetary R] 135.6 341.6
Angular size of the moon's orbit observed from the Earth*  [degrees] 0°53'00.82'' 2°13'33.08''

Angular diameter of the planet's disc as observed from the moon  [degrees] 0°50'41.83'' 0°20'07.71''
Brightness of the planet as observed from the moon**  [mag] –11.8 –9.8
Diameter of the moon's disc as observed from the planet's "surface"  [degrees] 0°00'00.06'' 0°00'00.03''
Brightness of the moon as observed from the planet's "surface"**  [mag] 13.9 15.9
Orbital velocity  [km/sec] 4.32 1.72
  * 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:
AstroNEWS – "Five dozen of the Jupiter's moons"
Monde des Monats – S/2003 J20
New Satellites of Jupiter 2003
The Astronomy Workshop – Satellite Viewer
Planetary Satellite Mean Orbital Parameters
Natural Satellite Physical Parameters