System I (±10° from equator)

9 hr 50 min 30 sec

System II (higher latitudes)

9 hr 55 min 41 sec

System III (magnetic field)

9 hr 55 min 29 sec

inclination of equator to orbit


dimensions of Great Red Spot

20,000 * 12,000 km

magnetic field strength at equator

4.3 gauss

number of known moons

more than 60

planetary ring system

1 main ring; 3 less-dense components

*Time required for the planet to return to the same position in the sky relative to the Sun as seen from Earth.

"Calculated for the altitude at which 1 bar of atmospheric pressure is exerted.

and the other inner planets, a deduction that is supported by detailed investigations of the giant planet's atmosphere and interior.

Three rotation periods, all within a few minutes of each other, have been established. The two periods called System I (9 hours 50 minutes 30 seconds) and System II (9 hours 55 minutes 41 seconds) are mean values and refer to the speed of rotation at the equator and at higher latitudes, respectively, as exhibited by features observed in the planet's visible cloud layers. Jupiter has no solid surface; the transition from the gaseous atmosphere to the fluid interior occurs gradually at great depths. Thus the variation in rotation period at different latitudes does not imply that the planet itself rotates with either of these mean velocities. In fact, the true rotation period of Jupiter is System III (9 hours 55 minutes 29 seconds). This is the period of rotation of Jupiter's magnetic field, first deduced from Earth-based observations at radio wavelengths and confirmed by direct spacecraft measurements. This period, which has been constant for 30 years of observation, applies to the massive interior of the planet, where the magnetic field is generated.

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