基于无量纲的轨道参数开展卫星性质统计研究

目前已发现了285颗围绕太阳系八大行星公转的卫星, 它们的轨道和物理性质呈现了丰富多样性. 目前为止, 几乎所有的卫星研究工作都基于单个卫星系统或者卫星群, 似乎缺少统一的研究. 提出了一个新的与行星性质无关、只与恒星半径有关的轨道参数n, 定义为以太阳半径为单位的轨道半长轴的自然对数. 不同行星的卫星的n值都存在双极分布, 绝大部分卫星在$n\gtrsim2$区间, 其次在$n\lesssim-1$区间, 位于中间区域的行星则很少. 从卫星物理参数和轨道参数与n的关系中发现, 分属六大行星的卫星有明显的共同特征. 首先, 轨道偏心率和轨道倾角偏大的卫星的n值都在3.5左右, 它们都是巨行星的不规则卫星. 其次, n值在-1和1之间的卫星绝大部分体积大、质量大、反照率高、自转速度慢. 从文献中找到11颗系外卫星候选体, 获得了它们轨道n值和卫星质量, 发现后者也是在-1< n< 1区间最大，其他区间偏小.这些统一的 规律暗示，太阳系内不同行星的卫星形成机制以及太阳系外卫星的形成机制可能一样或类似.

Statistical Study of the Planetary Satellites in the Framework of a Planet-irrelevant Orbit Parameter

Currently, 285 natural satellites orbiting the eight solar system major planets have been discovered, exhibiting a wide range of orbital and physical properties. Most previous studies of natural satellites focus only on satellites of one particular planet, or one satellite group. This paper introduces a new orbital parameter, denoted as ``n'', which is independent of planetary characteristics but dependent on stellar parameter. It is defined as the natural logarithm of the semi-major axis of the orbit in units of the solar radius. It is found that moons of the different planets all exhibit a bimodal distribution of n values, with the majority falling within the $n\gtrsim2$ range, followed by a smaller number within the $n\lesssim-1$ range, and very few located in the intermediate region. Analysis of satellite physical parameters and orbital parameters with respect to n reveals common features among satellites of the six major planets. Firstly, satellites with high orbital eccentricity and inclination tend to have n values around 3.5, and they are irregular satellites of the giant planets. Secondly, satellites with n values between $-1$ and 1 are typically characterized by large volume, high mass, high albedo, and slow rotation rates. In addition, we identified 11 candidate exomoon candidates from the literature and found that massive ones also tend to fall within the $-1 < n < 1$ range, with less massive ones in other ranges. These consistent patterns suggest that the formation mechanisms of satellites in the solar system for different planets and for the potential exomoons may share similar formation mechanism.