木卫三的动力学参数

A Study of Dynamical Parameters of Ganymede

:木卫三是太阳系中最大的一颗天然卫星。当伽利略飞船于 1996年 6月和 9月两次飞经木卫三时 ,定出了二阶带谐和扇谐 Stokes系数 J2 和 C2 2 。本文利用最新的木卫三的物理参数 ,首先建立了一组内部结构模型 ,然后估算出木卫三的若干动力学参数 ,并与月球的相应值进行比较 ,结果表明这两个天然卫星最显著的不同是 ,木卫三满足静力学平衡条件 。

Jupiter's satellite Ganymede is the largest satellite in the Solar system.The Galileo spacecraft when passing close to Ganymede in June and September 1996 resulted in determining the second zonal J2 and the second sectorial C22 Stokes parameters.Using the updated physical parameters,we constructed a group of internal models of Ganymede,and estimated some dynamical parameters for these models.By means of comparison with the Moon we make the following conclusions: 1.The moment-of-inertia factor,I/MR2=0.311,of Ganymede is the lowest yet obtained for any solid body in the solar system,and implies that Ganymede has an outer silicate core surrounding a melted metal (Fe or Fe-FeS) inner core. 2.The conclusion can be drawn about the hydrostatic equilibrium of Ganymede at present.That is to say,equation (13) hold true for Ganymede. 3.The calculated results for Ganymede and the Moon indicate that the two satellites are similar to each other in their dynamical flattening, 4.The parametric model,GA-1,listed in Table 5 of this paper can be used for reference in theoretical researches for the future.