Three rotation schemes for different parts of Jupiter. System I refers to the equatorial region of the planet's visible atmosphere, and System II to the rest of its atmosphere. The period of System I is 9 h 50 m 30.003 s, and that of System II is 9 h 55 m 40.632 s. These figures are derived from angular rotations of 877 °.90 and 870 °.27 in 24 hours, the latter representing the motion of the Great Red Spot in 1890–91. The systems are used for reference by visual observers, particularly when making longitude plots of visible surface markings. System III, derived from radio observations, refers to the rotation of the solid interior. Its period is 9 h 55 m 29.711 s.
Subjects: Astronomy and Astrophysics.