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  3. It turns out that measuring the distance to a star is an interesting problem

It turns out that measuring the distance to a star is an interesting problem

游客2023-07-11  55
问题     It turns out that measuring the distance to a star is an interesting problem! Astronomers have【S1】______up with two different techniques to estimate how far away any given star is.
    The first【S2】______uses triangulation(三角测量). The Earth’s【S3】______around the sun has a diameter of about 186 million miles(300 million kilometers ). By looking at a star one day and then looking at it again 6 months later, an astronomer can see a【S4】______in the viewing angle for the star. With a little trigonometry(三角学), the different angles yield a distance. This technique【S5】______for stars within about 400 light years of earth.
    There is no direct method currently【S6】______to measure the distance to stars【S7】______than 400 light years from Earth, so astronomers instead use brightness measurements. It turns out that a star’s color spectrum is a good indication of its actual brightness. The【S8】______between color and brightness was proven using the several thousand stars close enough to earth to have their distances【S9】______directly. Astronomers can therefore look at a distant star and determine its color spectrum. From the color, they can determine the star’s actual brightness. By knowing the actual brightness and comparing it to the【S10】______brightness seen from Earth(that is, by looking at how dim the star has become once its light reaches Earth), they can determine the distance to the star.

A)capable          B)works
C)put              D)difference
E)track            F)come
G)relationship     H)available
I)technique        J)measured
K)nearer           L)apparent
M)orbit            N)applies
O)farther [br] 【S9】
选项
答案 J
解析 从两方面判断，一是“have…done”结构，需用过去分词；二是文章在第1段和第3段的第1句均有“measure the distance”的提示。
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