我们太阳系的其他行星缺乏氧气大气层，这有助于解释为什么地球上存在生命。
Other planets in our solar system lack the oxygen atmosphere that helps explain why life exists on Earth.
当然，我们现在知道，包括地球在内的行星都围绕太阳公转，而太阳系只是宇宙的一小部分。
Of course, we now know that the planets, including Earth, revolve around the Sun, and that the solar system is only a tiny part of the universe.
我们的行星地球，连同其他行星，围绕我们的太阳旋转，这就是我们的太阳系。
Our planet Earth, together with other planets, revolve around our Sun in what is called our Solar system.
大多数已知的太阳系外行星都居住在高度拉长而非圆形的轨道上。
Most known extrasolar planets reside in highly elongated, not circular, orbits.
月球的自转和倾斜在太阳系的其他行星体中是独一无二的。
The Moon's spin and tilt are unique among other planetary bodies in the solar system.
这张图片展示太阳系9个行星中的6个行星。
The picture shows six of the nine planets in the solar system.
这是119颗太阳系外行星中的一颗。这些行星围绕除太阳外的其他星体运行。
The planet is one of 119 known extra-solar planets, objects that orbit stars other than the sun.
土星是太阳系的第二大的行星。
太阳占据了太阳系总质量的大约99.85%，而在剩余的0.15%中，行星占据了大部分。
An estimated 99.85 percent of the mass of our solar system is contained within the Sun, while the planets collectively make up most of the remaining 0.15 percent.
我们太阳系的有序特性使大多数天文学家得出结论，这些行星基本上在同一时间形成，且物质来源和太阳的一样。
The orderly nature of our solar system leads most astronomers to conclude that the planets formed at essentially the same time and from the same material as the Sun.
在火星和我们太阳系的其他行星上没有氧气，这意味着这些行星也缺乏保护地表生物免受紫外线辐射的臭氧层。
The absence of an oxygen atmosphere on Mars and other planets in our solar system means that these planets also lack an ozone shield that would protect surface-dwelling life from UV radiation.
复杂的生命在地球表面进化，而不是在火星或太阳系的其他行星上，因为在那些行星上，早期的地表生命被紫外线杀死了。
Complex life evolved on the Earth's surface, but not on Mars or other planets in the solar system because on those planets, early surface life was killed by UV radiation.
在我们的太阳系中，行星的轨道几乎是圆形的，这使得科学家们预测，其他恒星周围的行星也会位于圆形轨道上。
The nearly circular orbits of planets in our solar system led scientists to expect that planets around other stars would also reside in circular orbits.
目标是测量AU；随后，当我们知道了所有围绕太阳的其他行星的轨道速度，对太阳系的规模就有充分的认识了。
The goal was to measure the AU; then, knowing the orbital speeds of all the other planets around the Sun, the scale of the Solar System would fall into place.
我们的太阳系中的行星不是那些可以通过理论预测其组成的普通行星，而是独特的个体，它们的化学和构造特征都是由它们创造的。
Instead of normal planets whose composition could be predicted by theory, the planets populating our solar system are unique individuals whose chemical and tectonic identities were create.
木星、土星、天王星和海王星。这些都是气体行星，是太阳系的四个重量级。但曾经存在第五个行星吗？
Jupiter, Saturn, Uranus, and Neptune. Those are the gas giants, the four heavyweights of the solar system. But was there once a fifth?
矛盾的是，虽然液态水所需的温度只存在于太阳系内部，但生命的关键组成部分，包括水本身，却主要存在于小行星带之外。
Paradoxically, while the temperatures required for liquid water exist only in the inner solar system, the key building blocks of life, including water itself, occur primarily beyond the asteroid belt.
火星是太阳系中最轻的行星，这使得火星成为太阳系中第二小的行星。
Mars is the lightest planet in the solar system, which makes Mars the second smallest planet in the solar system.
科学家们已经发射了很多宇宙飞船去探索太阳系的其他行星。
Scientists have launched many spaceships to explore other planets in the solar system.
在太阳系所有行星中，火星绕太阳的轨道速度第四快。
Mars's orbit around the Sun is the fourth fastest orbit of all the solar system planets.
这一定义将会大大地加长太阳系行星的名单。
Such a definition would greatly expand the list of planets in the solar system.
天文学家将迅速将这颗地球大小的行星包围，在那里他们发现与我们的太阳系相似的行星系统。
Astronomers are quickly closing in on Earth-size planets elsewhere in the galaxy as they find planetary systems that look more and more like our solar system.
选择性附加理论写出它的高气体密度在早期太阳系，在行星的形成。
The selective accretion theory chalks it up to high gas density in the early solar system, during the planet's formation.
由于2006年对天体的重新大排位，冥王星失去了它的行星地位，水星就被列为太阳系中最小的行星。
Since the great reclassification of astronomical objects in 2006, which saw Pluto lose its planetary status, Mercury has been listed as the smallest planet in the solar system.
天文学家在Gliese 581周围已经发现了六颗行星——除了我们的太阳系之外，Gliese 581是人类发现行星最多的行星系。
Astronomers have now found six planets in orbit around Gliese 581 - the most discovered in a planetary system other than our own solar system.
我们的家园地球，是太阳系的第三颗行星。
毫无疑问，太阳系所有的行星将围绕木星运转，因为在太阳系的行星中木星的质量最大。
There can be no doubt that they would all begin to revolve around Jupiter, because that planet has the largest mass.
濒死恒星的观察值，它们的金属含量，以及它们如何影响到围绕它们旋转的行星，都能为我们的太阳系的命运提供线索。
Observations of dying stars, their metal content, and how they affect the planets around them could provide clues about the fate of our own solar system.
它还能帮助寻找太阳系以外的行星。
天文学家同样可以根据他们对地球构成、活动和历史的了解来了解其他行星甚至太阳系之外的行星。
Astronomers can also use a knowledge of Earth materials, processes and history to understand other planets - even those outside of our own solar system.
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