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冥王星挥泪降级 众行星痛失兄弟

冥王星挥泪降级 众行星痛失兄弟

 

IT is always hard for a small fish to live in a big pond. Pluto's recent departure from the classical planet family clearly proves that size really matters.   小鱼要在大池塘里生活下去通常是不太容易的。最近冥王星被从经典行星家族中除名就印证了这一点,体积大小真的事关重大。   Astronomers voted on August 24 to create the first scientific definition of the word "planet", and Pluto obviously didn't make the cut. It turned out to be only a "dwarf planet".     8月24日,经过天王学家们投票决定,“行星”一词第一次有了科学定义,显然冥王星无以幸免。它成为了唯一一颗“矮行星”。   After weeks of heated debate, over 2,500 astronomers from 75 countries voted on the definition of a "planet" at a conference of the International Astronomical Union (IAU). According to the definition, a planet must have a clear neighbourhood around its orbit. Pluto has widely been considered a planet since its discovery in 1930. Unfortunately, it has a special orbit which overlaps with Neptune's. It is all because, compared with Neptune, Pluto is very small. It is attracted by Neptune's gravity when the two planets get closer.     在国际天文学联合会上,经过几周的激烈讨论,来自75个国家的2500多名天文学家对“行星”的定义进行了投票。定义规定,行星必须能够清除其轨道附近的其它物体。自从1930年发现冥王星以来,就普遍认定它是一颗行星。然而不幸的是,冥王星的轨道很特殊,与海王星是相交的。而和海王星比起来,冥王星体积又太小。因此当两颗行星靠近时,冥王星就被海王星的引力吸过去了。   According to IAU, a "dwarf planet" should have an orbit around the Sun. It will not have a clear neighborhood around its orbit, and must not be a satellite. The new classification means that the science textbooks will have to be updated.     国际天文学联合会的意见认为,“矮行星”应该绕太阳沿轨道运转。但它不能清除其轨道附近的其它物体,而且不是卫星。这个新分类意味着科学教科书也需要更新了。   The solar system is now made up of the eight "classical planets," together with a number of dwarf planets. The classical planets are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.     现在,组成太阳系的成为了八颗“经典行星”和一些矮行星。这八颗经典行星分别是:水星、金星、火星、木星、土星、天王星和海王星。   The debate over Pluto's status started in 1992. After an advanced telescope was sent into space, astronomers started to find a belt of objects, which lies beyond Neptune. The belt contains nearly 1,000 objects, including Pluto. As they continued the exploration, scientists recently discovered at least 41 dwarf planets at the edges of the solar system. There are at least two objects of a similar size to Pluto.     其实关于冥王星的身份之争开始于1992年。在把一台先进望远镜送往太空之后,天文学家们开始在海王星之外发现了一条天体带。这个天体带中几乎有1000个天体,其中就包括冥王星。科学家们继续探索,最近又发现在太阳系周边至少有14颗矮行星。其中至少有2颗天体和冥王星的体积差不多。   It seems that even if the IAU had kept Pluto's status as a planet, the classical theory of nine planets in the solar system would have had to be changed, but the other way around. More dwarf planets of a similar size to Pluto would join the family of planets. Scientists will probably find many more dwarf planets.     由此看来,即使国际天文学联合会保住冥王星的行星地位,经典的太阳系九大行星理论也仍然要改,只是改法相反而已。将会有和冥王星体积相似的更多矮行星们加入到行星家族之中。或许,科学家们还会发现更多的矮行星。

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