" For all bodies except Ceres, the orbital data are for August 2006. For Ceres, the data are for September 2006. b Another orbital element is the time of any perihelion passage. For the Earth in 2006 this was at 15:00 UT on 4 January. c The Sun's axial inclination is with respect to the ecliptic plane.

d The rotation period of the Sun is at the equator: it increases with latitude, reaching about 36 days near the poles of the Sun. For Jupiter and Saturn it is for the deep interior.

"For the giant planets the equatorial radius is to the atmospheric altitude where the pressure is 105Pa (1 bar).

Table 1.2 Some properties of planetary satellites"'6

Objectc Some mean orbital elements Size, mass, mean density

Semimajor Sidereal Eccentricity Inclination/ °d Radius/kme Mass/1018 kg Mean axis/ 103 km period/days density/kg m-3



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