TOEFL Question
작성자
CLI 아카데미
작성일
2018-10-08 18:22
조회
819
Astronomy
Binary star systems are pairs of stars that move round the same center of mass n 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 system. Each type is classified according to how it is observed.
A visual binary 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.
Spectroscopic binary stars are systems that can only be seen with a spectrometer. The spectrometer is able to measure otherwise unperceivable difference in the type of light the stars emit. By watching for spectral lines, astrophysicists can recognize system in which the stars are too close together to be seen with a telescope.
An eclipsing binary star can be seen when the orbit of the binary is situated along the line of sight for the viewer. As the stars travel along their orbits, they inevitably eclipse each other. By studying eclipsing binaries, Scientists are able to learn about the distance to other galaxies with utmost accuracy. Thus, they can increase the available information concerning the composition of space.
Concentrate: to bring together; to focus
Resolving: relating to the ability to show thing 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
Q. The word they in paragraph 3 refers to
(A) galaxies
(B) eclipsing binaries
(C) scientists
(D) orbits
A>C