最常见的一种说法是它们可能包含来自其他行星的访客。
The most popular one is that they may contain visitors from other planets.
但我们知道，行星的情况不同。
发现系外行星的“黄金时代”。
目前用于寻找太阳系外行星的技术包括
The primary techniques currently used to find exoplanets include
这束X射线的强度暗示，它具有小行星的质量。
The x-ray intensity suggests it had the mass of a small planet.
行星的发现来自一瞬间。
这就意味着月球可以充当一个去其他行星的中转站。
This means the moon can act as a stepping stone to other planets.
这张艺术概念画展示了已知最小的拥有行星的恒星。
This artist's concept shows the smallest star known to host a planet.
天文学家早就认为，几大行星的轨道是可以预测的。
Astronomers had thought that the orbits of the planets were predictable.
该探测器第一次在木星这个气体行星的大气层里采样。
The probe was the first to sample the atmosphere of a gas planet.
当行星被巨大的陨石撞击时，它们离开了行星的表面。
They were blasted off that planet's surface when it was hit by huge meteorites.
他们估计这颗行星的质量大约是地球的5.9到7.5倍。
They estimated the planet's mass as 5.9 to 7.5 times that of Earth.
行星的光面(白昼侧)与太阳风有着最直接的接触。
The dayside has the most direct contact with the solar wind.
他们还看了来自火星这红色或带红色的行星的陨石。
They also saw meteorites known to have come from the red, or reddish, planet.
一旦质量超过这个限度，就开始进入气态巨行星的行列了。
Once the mass goes beyond that point, you start to get into gas giant territory.
这些已知行星的数量增至过去的2倍，并显示了这些行星的普遍存在。
That haul has more than doubled the number known, and suggests such planets are common.
首先是新行星的位置非常接近其所属恒星，其次，它虽小却相当沉重。
The first is its location so close to its parent star. Second, despite its size, it is quite heavy.
但是，直到今天，我们都没有“当场”捕捉到这种小行星对小行星的碰撞。
But until now, no such asteroid-asteroid collision has been caught "in the act".
约曼斯表示，在可预知的未来，对近地小行星的探测研究仍然会继续下去。
Still, Yeomans admits that the NEO search will likely continue for the foreseeable future.
这颗行星最终以罗马神话中的海神命名，称为海王星。
The planet was eventually named Neptune, after the Roman god of the sea.
她是一颗多么美丽的行星啊！
这颗行星有相对较薄的大气层，主要由氮气和氧气组成。
The planet has a relatively thin atmosphere composed mostly of nitrogen and oxygen.
对这个行星上的每个生命来说，那都是件好事。
And that would be good for every living creature on this planet.
印有“冥王星是一颗行星”字样的T恤衫正在热卖。
这就是行星地球，但是你不曾见过的样子。
This is planet Earth, but not as you have ever seen it before.
这是理解行星形成的关键。
目前尚未发现这样的行星，但它们很可能确实存在着。
Currently there have been no such planets discovered, but they are very likely to exist.
大多数行星都是在与母星赤道一致的平面上公转。
Most planets orbit in a plane that corresponds to their parent star's equator.
哪些行星可以维持生命的存在？
行星上的岩石也很重要。
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