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  3. 共用题干 So Many\"Earths\"The Milky Way（银河）co

共用题干 So Many\"Earths\"The Milky Way（银河）co

天天题库2019-12-17  14
问题 共用题干So Many"Earths"
The Milky Way（银河）contains billions of Earth-sized planets that could support life.That's the finding of a new study.It draws on data that came from NASA's top planet-hunting telescope.
A mechanical failure recently put that Kepler space telescope out of service.Kepler had played a big role in creating a census of planets orbiting some 170,000 stars.Its data have been helping astronomers predict how common planets are in our galaxy.The telescope focused on hunting planets that might have conditions similar to those on Earth.
The authors of a study,published in The Proceedings of the National Academy of Sciences,conclude that between 14 and 30 out of every 100 stars,with a mass and temperature similar to the Sun,may host a planet that could support life as we know it.Such a planet would have a diameter at least as large as Earth's,but no more than twice that big.The planet also would have to orbit in a star's habitable zone.That's where the surface temperature would allow any water to exist as a liquid.
The new estimate of how many planets might fit these conditions comes from studying more than 42,000 stars and identifying suitable worlds orbiting them.The scientists used those numbers to extrapolate（推算） to the rest of the stars that the telescope could not see.
The estimate is rough,the authors admit.If applied to the solar system,it would define as habitable a zone starting as close to the Sun as Venus and running to as far away as Mars.Neither planet is Earthlike (although either might have been in the distant past).Using tighter limits,the researchers estimate that between 4 and 8 out of every 100 sunlike stars could host an Earth-sized world.These are ones that would take 200 to 400 days to complete a yearly orbit.
Four out of every 100 sunlike stars doesn't sound like a big number.It would mean,however,that the Milky Way could host more than a billion Earth-sized planets with a chance for life.
选项 The Kepler space telescope has been in service for 15 years.A:Right B:Wrong C:Not mentioned
答案C
解析第二段第一句表明，近来的机械故障使开普勒太空望远镜不再为我们服务，通篇并没有提到开普勒太空望远镜为我们服务了多少年，所以选择C项。 第二段最后一句表明，开普勒太空望远镜主要关注与地球有相似环境的星球，所以选择A项。 第三段第二句表明，可以让生命存在的星球的直径至少要和地球的直径一样大，但不会超过地球直径的两倍。由此不难推断出其应该不比地球小，所以选择B项。 第三段第三、四句表明，适合人类居住的星球必须与它所环绕的恒星有一个适于居住的距离，以保证星球表面的温度能够允许液态水的存在。地球不仅适合人类居住，而且还绕着太阳运行。由此可知，题干表述正确。 第四段第一句表明，该项新评估源于对超过4.2万颗星球的分析，而非源于对17万颗星球的分析，所以选择B项。 第五段第一句表明，研究人员承认这项评估是粗糙的，即不精确的，所以选择A项。 文章第一段指出，这次的调查结果是新的发现，但通篇文章并未提到这是对可能有生命存在的星球的首次研究。
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