土星之后的下一颗行星是天王星。
火星是一颗行星，是离太阳第四近的行星。
Mars is a planet and is the fourth closest planet to the Sun.
一颗行星保持大气的能力取决于它的温度和质量。
A planet's ability to retain an atmosphere depends on its temperature and mass.
凝望天空中的同一颗行星，或草丛中闪烁的同一只萤火虫；
To gaze upon the same planet in space, or at the same glowworm gleaming in the grass;
经过长达六年的观测，发现有五颗行星的质量是地球的13-25倍。
Six years of observations revealed the presence of five planets between 13 and 25 times the mass of Earth.
简单地说，如果气体分子达到逃逸速度，它就能从一颗行星上“蒸发”。
Simply stated, a gas molecule can "evaporate" from a planet if it reaches a speed known as the escape velocity.
古代占星家认为宇宙由七颗行星统治；学过莎士比亚的人会记得，人的一生被分为七个时代。
The ancient astrologers believed that the universe was governed by seven planets; students of Shakespeare will recall that the life of man was divided into seven ages.
科学家们在前往另一颗行星的任务中发现的第一件事就是，金星根本不是小说中描绘的人间天堂。
The very first thing that scientists discovered with a mission to another planet was that Venus was not at all the earthly paradise that fiction had portrayed.
它只是颗行星，金星，我没记错的话。
我们的家园地球，是太阳系的第三颗行星。
我们知道在银河系内有几十亿颗行星。
We can tell in our galaxy there must be billions of planets.
冥王星该不该是颗行星？
你发现了多少颗行星？
按照官方说法，冥王星仍然算不上一颗行星。
哪颗行星是蓝色的？
欢迎来地球，一颗被称作太阳的恒星的第三颗行星。
Welcome to planet Earth, the third planet from a star named the Sun.
一颗行星与两颗恒星能够组成一个稳定的旋转系统。
“A pirouette of two stars and a planet can be stable, ” explains Dr Koch.
印有“冥王星是一颗行星”字样的T恤衫正在热卖。
然而就在最近，他们发现有颗行星成功地逃脱了此般厄运。
Recently, though, they have spotted somewhere that has managed to avoid such a fate.
人类踏上另一颗行星将是是最伟大的探险活动与历史丰碑。
Having a human actually set foot on another planet would be one of the greatest adventures possible, one of the greatest monuments to history.
论文提到了Gliese 581附近新发现的两颗行星。
The paper reports the discovery of two new planets around Gliese 581.
这里有趣的是在科学家发现这两颗行星之前，占星学都没有提及它们。
The interesting thing here is that until the scientific discovery of the two new planets, astrologers had not once mentioned them.
有可能维持生命存在的Gliese 581g为第四颗行星。
如果你在适合居住地带发现了一颗行星，就能说明这里有生命吗？
Because if you found one in the habitable zone, would that mean it had life?
但是，发现一颗特别恒星被多于一颗行星围绕的情况却很不常见。
But only occasionally is more than one found orbiting any particular star.
在1846年，人们确定了另一个发现，即太阳系中的第八颗行星。
In 1846, another discovery was confirmed, the eighth planet in the solar system.
最接近它的四颗行星是石质的类地行星——水星、金星、地球和火星。
The four planets nearest it are rocky, terrestrial worlds — Mercury, Venus, Earth and Mars.
这六颗行星都比地球要大，而且很可能由岩石物质和气体混合物组成。
All six are larger than Earth and are likely composed of mixtures of rocky material and gas.
不过，问题出现了：波德定则预测，火星和木星之间还应有一颗行星。
But there was a problem: Bode's law predicted that there ought to be a planet between Mars and Jupiter.
不过，问题出现了：波德定则预测，火星和木星之间还应有一颗行星。
But there was a problem: Bode's law predicted that there ought to be a planet between Mars and Jupiter.
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