托福阅读精练加试集锦【星体的形成】.docxVIP

智课网TOEFL备考资料 托福阅读精练加试集锦【星体的形成】 摘要： 托福阅读加试和托福听力加试是托福考试过程中我们最常遇到的一类题型，不少学生由于托福阅读加试不计入总成绩，而忽略了其重要性，其结果往往惨不忍睹，比实际估算的分数少很多，而今天，小编就来为大家详细的介绍一下有关托福阅读精练加试的相关内容，希望对你的托福阅读考试会有一定的帮助。  托福 阅读精练加试集锦：  how stars originated. first son exploded to dust and gas, stars accumulate the gas and crust , that’s why some planets are alike.other planet differ…  补充知识：    STARS  A star develops from a giant, slowly rotating cloud that consists almost entirely of the chemical elements hydrogen and helium.Due to the force of its own gravity, the cloud begins to collapse inward, thereby becoming smaller. As the cloud shrinks, it rotates more and more rapidly, just as spinning ice skaters turn more rapidly when they pull in their arms.  Stars are balls of gas that shine or used to shine because of nuclear fusion in their cores.  The most familiar star is the Sun. The nuclear fusion in stars produces a force that pushes the material in a star outward. However,the gravitational attraction of the star’s material for itself pulls the material inward.  A star can remain stable as long as the outward pressure and gravitational force balance.  Astronomers study stars by measuring their brightness or, with more difficulty, their distances from Earth. They measure the “color” of a star—the differences in the star’s brightness from one part of the spectrum to another—to determine its temperature.  They also study the spectrum of a star’s light to determine not only the temperature, but also the chemical makeup of the star’s outer layers.  Stellar evolution  The Sun is a type of star known as a main-sequence star. Eventually,main-sequence stars such as the Sun swell into giant stars and then evolve into tiny, dense, white dwarf stars. Main-sequence stars and giants have a role in the behavior of most variable stars and novas. A star much more massive than the Sun will become a supergiant star,then exp