七是土星的第八大卫星，也是土星已命名的48个卫星中最大的形状不规则卫星。
It is the eighth-largest satellite and the largest irregularly-shaped satellite of the 48 named Saturnian moons.
2010年3月3日，“卡西尼”号与土卫十二“海伦”这颗形状不规则的卫星亲密接触。
On March 3, 2010, Cassini got up close and personal with Helene, an irregularly shaped moon of Saturn.
大多数有着不规则轨道的卫星被认为是被恒星的重力所吸引住的彗星或者小行星，并且海卫二可能也是这样的。
Most moons with irregular orbits are thought to be former comets or asteroids captured by their parent planet's gravity, and that may be Nereid's story too.
大多数有着不规则轨道的卫星被认为是被恒星的重力所吸引住的彗星或者小行星，并且海卫二可能也是这样的。
Most moons with irregular orbits are thought to be former comets or asteroids captured by their parent planet's gravity, and that may be Nereid's story too.
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