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  3. About 2,500 of so-called supernovae are known inside our galaxy and beyond. But exactly what they were before they exploded is n

About 2,500 of so-called supernovae are known inside our galaxy and beyond. But exactly what they were before they exploded is n

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问题     About 2,500 of so-called supernovae are known inside our galaxy and beyond. But exactly what they were before they exploded is not so clear. The hunt for supernovae, from their origins to their long-term effects, is heating up rapidly. Understanding these incendiary objects is important in part because they are responsible for creating most of the elements in the universe, including the stuff of which people, plants and planets are made. A supernova is relatively easy to detect because of the intense radiation it casts off in visible light and other wavelengths. Figuring out what the star looked like prior to the explosion, however, requires probing into the archives of astronomy.
    A separate team of supernova hunters did just that, using a decade of Hubble Space Telescope images to search for possible pre-supernova stars. Their new findings support existing theory of supernova mechanics, which holds that only very massive stars explode. When a massive star burns up all its hydrogen fuel, it casts its outer layers into space and then collapses into a dense neutron star or black hole. Theorists believe that stars must be about 10 to 20 times the mass of the sun to support such an explosive scenario. Such heavy objects have brief lives, typically less than 20 million years, compared with the sun, which is middle-aged and already 4. 6 billion years old.
Ground-based telescopes that observed the actual supernova explosions are not as accurate as Hubble, however, due to air turbulence, so scientists require follow-up Hubble observations to see if they are in the right positions. One has already been eliminated, Alexei Filippenko of the University of California at Berkeley said, but he’s confident at least a couple of the remaining five will prove to be actual precursor stars. Astronomers have known for decades that the universe is expanding. But in the late 1990s they began to realize that the expansion is occurring at an ever-faster rate. This suggests that some mysterious, unseen force is at work across great distances, breaking the will of gravity that would otherwise rein in the universe eventually.
    Supernovae are useful in this research because they can be seen from far away. Astronomers measure how much an exploded star’s light has stretched, which tells them the speed at which the object is receding. By comparing this to nearby supernovae, researchers can refine the universal expansion’s rate of acceleration. In particular, the orbiting observatory’s keen new eyesight can be used to analyze pinpricks of light from very distant objects and learn what they are and what they’re made of. This so-called spectroscopy technique is just like using a prism to break white light into its constituent colors.
From the research of a team of supernova hunters we can infer that
选项 A、searching for explosion of the pre-supernova stars is essential.
B、researchers can refine the universal expansion’s rate of acceleration.
C、only stars about 10 to 20 times the mass of the sun can explode.
D、to observe actual supernova explosions, scientists require follow-up Hubble observations.
答案A
解析 从超新星考察队的研究中，我们可以推断出[A]探究超新星的爆炸非常重要。[B]研究人员可以更加精确地计算宇宙膨胀的加速率。[C]只有太阳质量约10到20倍的巨星才能爆炸。[D]为观测超新星的爆炸，科学家们需要哈勃望远镜来进行后续观察。文章第二段指出，一个考察队利用10个哈勃太空望远镜想探究超新星爆炸前的状况，他们的新发现证实了现有的超新星构成理论，这种理论认为只有巨星才能爆炸。从这段话，我们可以推断探究超新星的爆炸非常重要，所以，正确答案是[A]。[B]不正确，文章最后一段说“将这与附近的超新星相比较，研究人员可以更加精确地计算宇宙膨胀的加速率”，但从这个命题无法推断出“研究人员可以更加精确地计算宇宙膨胀的加速率”；[C]是文章明确指出的天文学家的发现，而不是引申；[D]不正确，文章第三段指出，因为空气湍流，所以用来观察真实的超新星爆炸的陆基望远镜不像哈勃望远镜那样准确，因此，科学家们需要哈勃望远镜来补充观测数据以察看它们的位置是否准确。从天文学家的发现无法推断此结果。
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