TOEFL Sample Question
작성자
CLI 아카데미
작성일
2013-02-07 16:04
조회
4315
Read the following passage. Then fill in the diagram with the information that you read.
Binary Star System
Binary star systems are pairs of stars that move around the same center of mass in space. To explain further, the center of mass is the point on which the mass of a system is concentrated. By studying binary stars, astrophysicists are able to determine the actual mass of stars in the system. There are several types of binary star systems. Each type is classified according to how it is observed.
A visual binary star is one that can be seen through a telescope. Sometimes binary stars cannot be seen through a telescope because they are too close together and simply appear as one star. However, many modern telescopes with high resolving power can distinguish between binary stars. The brighter of the visual binary is called the primary star, and the dimmer is called the secondary star. By measuring the angles of the stars in relation to each other over time, physicists are able to determine the shape of the binary’s orbit.
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concentrate : to bring together ; to focus
resolving : relating to the ability to show things in detail
orbit : a path that objects move around
unperceivable : not able to be noticed
spectral line : a dark or bright line that is emitted from a continuous spectrum
inevitably : in a way that cannot be avoided
composition : the parts that something is made of
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Q. The word it in paragraph refers to
(A) mass
(B) type
(C) star
(D) system
A> (B) type