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  3. 共用题干 So Many"Earths"The Milky Way（银河）contains billions of Earth-sized plan...Th

共用题干 So Many"Earths"The Milky Way（银河）contains billions of Earth-sized plan...Th

admin2020-12-24  9
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 main task of the Kepler space telescope is to find out planets with similar conditions to Earth's.
A:Right
B:Wrong
C:Not mentioned
答案A
解析本篇文章只在第二段第一句表明，近来一次机械故障使开普勒太空望远镜不再为我们服务，并没有提到开普勒太空望远镜为我们服务了多少年。
第二段最后一句表明，开普勒太空望远镜主要寻找与地球有相似环境的星球。
第三段第二句表明，可让生命存在的星球的直径至少与地球的直径一样大，但不会超过地球直径的两倍。由此可推测出其不会比地球小，因此题干表述错误。
第三段第三、四句表明，适合生命存在的星球必须与它所环绕的恒星有一个合适的距离，以保证星球表面的温度允许液态水存在，而地球正是适合人类居住的星球，而且地球是绕着太阳运行的。
第四段第一句表明，这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。
第五段第一句表明，研究者承认这项评估是粗糙的，即不精确的。
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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