托福阅读天文类词汇科普:恒星的“退休”生活大揭秘!附托福天文类词汇资料免费领取!

最近“延迟退休”的新闻刷屏，90后00后要一直工作到65岁才能和姐妹们相约广场舞，想必让大家都有些emo。我就想着做两篇托福阅读压压惊，结果竟然读到了星星的“退休”生活，今天就给大家科普一些相关的托福阅读天文类常考话题。每一颗恒星都曾有过它的高光时刻，但当它们耗尽了内部的核燃料，这些曾经的宇宙巨星们会去哪里“安度晚年”呢？一起揭开恒星遗迹（Stellar Remnants）的神秘面纱吧！

🚀 恒星的生命周期：从辉煌到遗迹

每颗恒星都从尘埃和气体的星云nebula中诞生，经历漫长的岁月，耗尽核燃料nuclear fuel，最终走向死亡。在这个过程中，它们可能会变成以下3种恒星遗迹：

白矮星（White Dwarfs）
中子星（Neutron Stars）
黑洞（Black Holes）

Eventually, all stars consume their nuclear fuel and collapse into one of three final states-white dwarf, neutron star, or black hole.

（TPO73-3 Stellar Remnants）

👵 白矮星（White Dwarfs）：宇宙中的“小老太”

当一颗类太阳恒星（低或中等质量的恒星）耗尽其核燃料后，它会坍缩（collapse）成了一个“小老太”——白矮星。它们虽然体积小，但密度（density）大得惊人，一茶匙的白矮星物质（matter）在地球上的重量就能达到数十亿吨！白矮星的表面温度非常高且明亮（hot and bright），但它们没有核反应，所以只能慢慢冷却（cool and dim），最终变成一颗冷冰冰的“黑矮星”（ black dwarf）。不过别担心，我们的宇宙还太年轻，至今还没有出现过真正的黑矮星。

White dwarfs are extremely small stars with densities greater than any known terrestrial material. It is believed that white dwarfs began life as low-mass or medium-mass stars. As the star ages, it begins to collapse-become a “dwarf-because it no longer produces sufficient radiant heat to counteract the contracting force of its gravity.

Although some white dwarfs are no larger than Earth, the mass of such a dwarf can equal 1.4 times that of the Sun. A spoonful of such matter would weigh several tons.

As a star contracts into a white dwarf, its surface becomes very hot and very bright. But, without a continuing source of energy, it will slowly become cooler and dimmer. Although none have been observed, the terminal stage of a white dwarf must be a small, cold, non-luminous body called a black dwarf.

（TPO73-3 Stellar Remnants）

💪 中子星（Neutron Stars）：宇宙“肌肉男”

如果恒星的质量足够大（通常至少是太阳质量的8倍以上），它可能会经历一场超新星爆炸（Supernova event），其核心可能会坍缩成中子星。这些宇宙“肌肉男”的密度堪比原子核（atomic nucleus），一个中子星的直径只有几十公里，但质量却可能超过太阳！中子星的有着强大的磁场（strong magnetic field）和极高的旋转（rotate）速度。

Extending this idea of larger stars collapsing to smaller stars leads to the prediction that very large stars would collapse to stars even smaller and more massive than white dwarfs. Named neutron stars, these objects are thought to be the remnants of supernova events (the collapse of a large, very massive star). Neutron stars can be thought of as large atomic nuclei.

Although neutron stars have high surface temperatures, their small size would greatly limit their luminosity. Consequently, locating one visually would be extremely difficult. However, theory predicts that a neutron star would have a very strong magnetic field.

Further, as a star collapses, it will rotate faster, for the same reason ice-skaters rotate faster as they pull in their arms. If the Sun were to collapse to the size of a neutron star, it would increase its rate of rotation from once every 25 days to nearly 1,000 times per second.

（TPO73-3 Stellar Remnants）

🌀 黑洞（Black Holes）：宇宙的“终极BOSS”

如果恒星的质量非常大，它可能会经历更为极端的坍缩，变成宇宙的“终极BOSS”——黑洞。黑洞是如此密集（dense），以至于它们的引力强大（immense gravity）到连光都无法逃脱。

Are neutron stars made of the densest matter possible? No. During a supernova event, remnants of stars greater than three solar masses apparently collapse into objects even smaller and denser than neutron stars. Even though these objects would be very hot, their gravity would be so immense that even light could not escape the surface.

Consequently, they would literally disappear from sight. These incredible bodies have appropriately been named black holes. Anything that moved too near a black hole would be swept in by its irresistible gravity and annihilated.

（TPO73-3 Stellar Remnants）

除了白矮星、中子星、黑洞三种恒星遗迹外，还有一些天文学科名词经常和它们伴随出现：

🌑 黑矮星（Black Dwarf）：白矮星的最终状态

虽然目前宇宙中还没有黑矮星，但理论上，当白矮星冷却到足够低的温度后，就会变成黑矮星，这是它们的最终状态。

🌠 脉冲星（Pulsar）：中子星的活跃形态

脉冲星是快速自转的中子星，它们以极其规律的周期释放电磁辐射束（radiates pulses of radio energy）。如果这些辐射束（beam）指向地球，我们就可以将它们识别为脉冲星。脉冲星的发现是20世纪天文学的重要成就之一。

🔥 超新星（Supernova）：恒星的壮丽谢幕

超新星爆炸supernova explosion是宇宙中最壮观的事件之一，它是大质量恒星生命的终结，也是中子星或黑洞诞生的瞬间。当一颗大质量恒星耗尽其核燃料，它的核心可能会突然坍缩collapse，导致外层物质以极高的速度被抛向太空，产生一场壮观的爆炸。

🌌 星云（Nebula）：恒星的摇篮和坟墓

星云是星际空间中的云雾状天体，由尘埃（dust）、氢气（hydrogen）、氦气（helium）和其他离子化气体（ionized gases）组成。它们可以是恒星的孕育地，如创生之柱（Pillars of Creation）；也可以是恒星死亡后的遗留物，如行星状星云（Planetary Nebula）。

这些天体之间的关系要怎么去理解呢？可以用恒星的质量和它们生命终结时的行为来概括。低质量恒星通常会变成白矮星，而高质量恒星可能会经历超新星爆炸，变成中子星或黑洞。黑矮星是白矮星的生命最终状态，脉冲星是高度活跃的中子星。星云在恒星的生命周期中扮演着双重角色，既是恒星的诞生之地，也是它们死亡后的坟墓。

天文学科的文章一直是同学们的头号公敌，生词多，概念复杂且陌生，考试时候遇到了没有一点学科背景知识的只能全靠现场猜。

虽说托福阅读主要考察的是咱们对长难句理解和文章逻辑结构的把握，但是木有一点学科背景的加持，做题速度和准确度肯定要下降，想拿到25+的高分就更难了。所以还是要通过多读多练相关文章，把这块知识点给熟悉起来，参考以下TPO天文类文章目录练起来吧，老师把《托福阅读学科词汇-天文类》也准备好了，抓紧看起来吧～