NASA发布了开普勒太空望远镜的一项新发现，暗示发现了人类几千年来梦寐以求的“另一颗地球”。那么，关于地球“大表哥”，我们都确切知道些什么呢？

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NASA's Kepler mission has confirmed the first near-Earth-size planet in the “habitable zone” around a sun-like star. This discovery and the introduction of 11 other new small habitable zone candidate planets mark another milestone in the journey to finding another “Earth.”
美国国家航空航天局（NASA）的开普勒太空望远镜在类太阳恒星周围的宜居带中，首次发现了和地球大小近似的行星存在。这项发现连同其他11个新的行星候选者一起，奠定了人类寻找“新地球”漫漫长路上的又一个里程碑。

The newly discovered Kepler-452b is the smallest planet to date discovered orbiting in the habitable zone -- the area around a star where liquid water could pool on the surface of an orbiting planet -- of a G2-type star, like our sun. The confirmation of Kepler-452b brings the total number of confirmed planets to 1,030.
开普勒452b是迄今为止发现的宜居带内最小的行星。宜居带指的是距离恒星不远不近的一个环带，在该环境中，液态水可在行星的表面保存。开普勒452b的发现使已确认系外行星的数量增加到1030颗。

Kepler Space Telescope
开普勒太空望远镜

Let’s start with NASA’s Kepler Space Telescope, an observatory in space dedicated to finding planets outside our solar system, particularly alien planets that are around the same size as Earth in the "habitable" regions of their parent star. First launched in 2009, by now, it has found more than one thousand planets outside the solar system, contributing greatly to our knowledge of the outer space.
首先我们先从开普勒太空望远镜说起，这是美国国家航空航天局设计的太空望远镜，它的主要任务是寻找环绕着其他恒星之类地行星，在2009年发射之后发现了上千颗系外行星，几乎把我们已知的系外行星数提升了一个量级。

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Planet & Star
行星和恒星

A star is a celestial body of hot gases that radiates energy derived from thermonuclear reactions in the interior, like the sun; a planet is a celestial body (other than comets or satellites) that revolves around a star and emits no light, like the earth. The Kepler Space Telescope surprised us in many ways. We now know that among the monitored sun-like stars, 2/3 of them change actively in terms of brightness, indicating that they are more active than we imagined. Orbiting around these starts, more planets of the similar size of the earth are discovered.
恒星是指宇宙中靠核聚变产生的能量而自身能发热发光的星体，比如太阳；而行星是自身不发光、环绕着恒星的天体，比如地球。开普勒望远镜带来的最大惊喜之一就是，在我们监测的类似太阳的恒星里，有2/3在亮度方面的变化幅度都比太阳要大，说明这些恒星比我们想象的更活跃。这些发现帮助我们找到了和地球大小类似的行星，而它也正围绕着像太阳一样的恒星转动。

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Earth-like Planet
类地行星

Earth-like planets are similar in structure: there is a core composed of metal (mainly iron), and the surface is mainly covered by silicate. The moon has a similar structure, but its core has not enough Fe. The Kepler Space Telescope has detected many possible earth-like planets, Kepler-452b being one of them.
类地行星的构造都很相似：中央是一个以铁为主，且大部分为金属的核心，围绕在周围的是以硅酸盐为主的地凾。月球的构造也相似，但核心缺乏铁质。开普勒太空望远镜收集和传输的潜在类地行星中就包括开普勒452b。

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the Closest Twin to Earth
孪生星球

The planet takes 385 days to orbit its star. It is older and bigger than earth, and has a probable mass five times that of earth, and its surface gravity is twice earth's. It is not clear if Kepler-452b offers habitable environments. It orbits a sun-like star which is six billion years old, making it 1.5 billion years older than the sun. At this point in its star's evolution, Kepler-452b is receiving ten percent more energy from its parent star than earth is currently receiving from the sun.
这颗行星的公转周期为385天，无论是体积还是年龄，都比地球大。它的质量大约是地球的五倍，重力为地球的两倍。目前还无法确定开普勒452b是否适宜生命居住。开普勒452b围绕着一颗与太阳相似的恒星运转，这颗母星的“年龄”为60亿岁，比太阳“老”15亿岁。在我们观测到的这颗母星所处的演变状态，开普勒452b从它那里接收的能量比地球从太阳接收的能量多10%。

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Habitable-zone
宜居带

Habitable-zone is the region around a star within which planetary-mass objects with sufficient atmospheric pressure can support liquid water at their surfaces. Due to the importance of liquid water to life as it exists on earth, the nature of the habitable-zone and the objects within is believed to be instrumental in determining the scope and distribution of earth-like extraterrestrial life and intelligence.“
宜居带”是指一颗恒星周围的一定范围，在这一范围内行星能够保持一定气压，使其表面的水可以以液态形式存在，因为液态水被认为是生命生存所不可缺少的元素，因此我们认为“宜居带”的性质和其中的行星决定了类地行星上智慧生命存在的范围和分布情况。

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Constellation Cygnus
天鹅座

Kepler 452b, about 1,400 light years from earth in the constellation Cygnus, is the first to be confirmed the near-Earth-size planet in the "habitable zone" around a parent star. the constellations Cygnus, Lyra and Aquila will have risen well up into the south-east, Their three brightest stars respectivly make up the "Summer Triangle".
开普勒452b在距离地球1400光年的天鹅座，位于宜居带，围绕着一颗母星运转。天鹅座与银河两岸的天琴座和天鹰座鼎足而立，这三个星座在东南方向升起，它们的三颗主星组成了“夏季大三角”。

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