我认为这可能是因为奥尔特云受到一个正在把彗星抛出不变轨道的大天体的扰动，其一一小部门彗星可能会达到地球。

I believe it is likely that this is because the Oort Cloud is being disturbed by a massive body that is throwing comets out of stable orbits, a small fraction of which could reach the Earth.

youdao

目前，它正在与地球相对位置不变的轨道接受严格的测试，希望2008年第1季度提供服务。

It is now in geosynchronous orbit undergoing rigorous testing and is expected to begin service in the first quarter of 2008.

youdao

研究了基于三体问题的不变流形设计低成本登月轨道的问题。

The low-energy lunar landing trajectory design using the invariant manifolds of restricted three body problem is studied.

youdao