积累一定的背景知识也可以很好的帮助我们提高做托福阅读题目的效率，今天新航道的小编就给大家科普一些托福阅读篇章中天文类文章的背景知识，下面我们一起来看看吧。
1、天文学文章中常涉及的相关背景
①各大行星的发现过程或研究现状
②各大行星的地质或者大气情况
2、文章中常涉及的天体
有恒星（star，形容词stellar）：恒星是由引力凝聚在一起的一颗球型发光等离子体，比如太阳（the Sun）。
八大行星：按照和太阳的距离，它们依次为水星（Mercury，离太阳近，好热啊）、金星（Venus，和地球最像，但是还是好热）、地球（Earth）、火星（Mars）、木星（Jupiter）、土星（Saturn）、天王星（Uranus，）、海王星（Neptune）。
TPO阅读中就有一篇对比类地行星（terrestrial planets）和类木行星（Jovian planets）的文章，比较了两类行星的大气，质量，温度等各个因素的不同点。
Paragraph 5: The Jovian planets have very thick atmospheres consisting of varying amounts of hydrogen, helium, methane, and ammonia. By comparison, the terrestrial planets have meager atmospheres at best. A planet's ability to retain an atmosphere depends on its temperature and mass. Simply stated, a gas molecule can "evaporate" from a planet if it reaches a speed known as the escape velocity. For Earth, this velocity is 11 kilometers per second. Any material, including a rocket, must reach this speed before it can leave Earth and go into space. The Jovian planets, because of their greater masses and thus higher surface gravities, have higher escape velocities (21-60 kilometers per second) than the terrestrial planets. Consequently, it is more difficult for gases to "evaporate" from them. Also, because the molecular motion of a gas depends on temperature, at the low temperatures of the Jovian planets even the lightest gases are unlikely to acquire the speed needed to escape. On the other hand, a comparatively warm body with a small surface gravity, like Earth's moon, is unable to hold even the heaviest gas and thus lacks an atmosphere. The slightly larger terrestrial planets Earth, Venus, and Mars retain some heavy gases like carbon dioxide, but even their atmospheres make up only an infinitesimally small portion of their total mass.
1.According to paragraph 5, which of the following statements is true of both Jovian and terrestrial planets?
○The thicker the atmosphere, the smaller the planet’s mass
○The more varied the gases in the atmosphere, the higher the temperature
○The higher the surface gravity, the higher the escape velocity
○The less the atmosphere contributes to the total mass, the lower the temperature
2.According to paragraph 5, what is a major reason that Jovian planets have much thicker atmospheres than terrestrial planets do?
○Jovian planets have lower surface gravities
○Jovian planets have lower temperatures
○Jovian planets have lower escape velocities
○Jovian planets’ gas molecules have higher average speeds
3.Paragraph 5 supports which of the following statements about the ability of planets to retain gases?
○More-massive planets are less able to retain gases than less-massive ones.
○Planets are more likely to retain heavy gases than light gases.
○Jovian planets are unlikely to retain the lightest gases.
○Only terrestrial planets have been able to retain carbon dioxide.
看题之前，先来了解一下2个分类，类地行星（terrestrial planets）和类木行星（Jovian planets）。前者包括：水星（Mercury）、金星（Venus）、地球（Earth）、火星（Mars）：类地行星是与地球相类似的行星。它们距离太阳近，体积和质量都较小，平均密度较大，表面温度较高，大小与地球差不多，也都是由岩石构成的。后者包括：木星（Jupiter）、土星（Saturn）、天王星（Uranus）、海王星（Neptune）。2类行星在大气层厚度，温度，行星质量和引力方面都不尽相同。
上面的段落就是依据这些不同而展开。题1，which of the following statements is true of both Jovian and terrestrial planets? 对应全段落，判断选项对错，属于全段落的事实信息题。根据原文内容“The Jovian planets, because of their greater masses and thus higher surface gravities, have higher escape velocities (21-60 kilometers per second) than the terrestrial planets. ”，选项c是正确的，即引力越大，逃逸速度越高。选项对应的知识点，如果事先有所了解，做题也会事半功倍。另外的2题欢迎同学们评论区答题。
如果你想了解更多的雅思托福课程，留学规划或者有任何疑问，欢迎联系新航道重庆学校。
新航道重庆学校官网：cq.xhd.cn
新航道重庆学校电话：400-185-9090
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