On 15 September, a team of Chinese astronomers reported a rare find. Using the Five-hundred-metre Aperture Spherical radio Telescope, known as FAST, they discovered a pair of neutron stars called PSR J1856-0039. The two stars circle each other once every 2.36 hours, one of the shortest orbital periods ever recorded. Their total mass is only 2.488 times that of the sun, the lightest such pair ever confirmed. The study appeared in Physical Review Letters.
Neutron stars are the remains of very large stars that died in supernova explosions. They are only about twenty kilometres across, yet they can weigh more than the sun. Some send out radio signals at extremely regular intervals, and astronomers call them cosmic clocks. Two neutron stars orbiting each other form a system that is very hard to find. Only about thirty are known.
The value of such systems lies in what happens at the end. When the two stars finally meet, they send out gravitational waves and produce heavy elements such as gold and platinum. Short orbital periods are especially valuable, because the stars sit closer, gravity grows stronger, and the merger comes sooner. Here the visible pulsar weighs about 1.30 solar masses and its companion about 1.19, making the companion one of the lightest neutron stars ever seen.
The very tight orbit also gave scientists a natural laboratory. They observed several effects that Albert Einstein predicted. The oval orbit slowly turns, light escaping the strong gravity is stretched towards redder colours, time passes a little more slowly, and the orbit shrinks as gravitational waves carry energy away. The measured shrinking matched the theory closely. The system may also help astronomers detect frame dragging, in which a spinning star drags the space around it.
Astronomers believe the two stars will merge in about 82 million years, most likely forming a heavier neutron star. FAST has already found around 900 new pulsars, and each unusual system adds another piece to our understanding of matter and of where the heaviest elements come from.
Words to know:
- astronomer (天文学家)
- telescope (望远镜)
- orbital (轨道的)
- gravity (重力，引力)
- merge (合并，并合)
- companion (伴星；同伴)
- shrink (缩小，收缩)
- element (元素)
长难句拆解 · 多个并列分句 + as 引导状语从句
例句：The oval orbit slowly turns, light escaping the strong gravity is stretched towards redder colours, time passes a little more slowly, and the orbit shrinks as gravitational waves carry energy away.
这句话由四个并列分句组成，最后用 and 收尾，是典型的「清单式长句」。读的时候先数逗号，把四项分开：① the oval orbit slowly turns ② light … is stretched towards redder colours ③ time passes a little more slowly ④ the orbit shrinks。四项都在描述同一件事——强引力环境下的相对论效应。
第二项里的 escaping the strong gravity 是现在分词短语作后置定语，修饰 light，等于 light that escapes the strong gravity；is stretched 是被动语态，表示「光被拉伸」。第四项末尾的 as gravitational waves carry energy away 是时间状语从句，as 在这里意为「随着」。
直译：椭圆轨道缓慢地转动，逃离强引力的光被拉向更红的颜色，时间流逝得稍稍更慢，而随着引力波带走能量，轨道也在收缩。
同义替换 · 雅思阅读利器
下面 6 组替换都出自本文，右侧是对应的替换说法，点开核对。
- reported a rare find → announced an unusual discovery（表示「报告罕见发现」）
- circle each other → orbit one another / go around each other（表示「相互绕转」）
- hard to find → difficult to detect / rarely seen（表示「难以发现」）
- The value of such systems lies in → Such systems matter because of（表示「价值在于」）
- matched the theory closely → agreed closely with the theory（表示「与理论高度吻合」）
- adds another piece to our understanding → helps us understand a little more（表示「为理解补上一块」）
阅读自测 · 3 题
三道题分别对应细节、因果与词义，先不看答案。
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- 判断正误（T / F / NG）：The two neutron stars complete one orbit every 2.36 days.
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- 简答：Why are short orbital periods especially valuable to scientists?
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- 选词填空：When the two neutron stars meet, they produce heavy elements such as ______.（A. gold and platinum B. iron and copper C. oxygen and nitrogen）
参考答案与解析
每题给出答案与判断依据，注意最后提到的干扰项套路。
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- F（错误）。第一段写 circle each other once every 2.36 hours，单位是小时，不是天。这是典型的「偷换单位」干扰项：数字 2.36 原封不动照抄，只把 hours 换成 days，扫读时最容易漏看。
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- Because the stars sit closer, gravity grows stronger, and the merger comes sooner. 依据在第三段第三句，属于因果关系题，答句用 Because 开头最稳妥，三个要点都出自同一个原因状语从句。
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- A. gold and platinum。第三段写 they produce heavy elements such as gold and platinum。铁、铜、氧、氮都是常见元素，与文中「重元素来自中子星并合」的论述不符，属于「常识合理但原文未提」的干扰套路。
中文译文
9 月 15 日，一支中国天文学家团队报告了一项罕见发现。他们利用五百米口径球面射电望远镜（即中国天眼 FAST），发现了一个名为 PSR J1856-0039 的双中子星系统。这两颗星彼此绕转一圈只需 2.36 小时，是人类已知最短的轨道周期之一。它们的总质量仅为太阳的 2.488 倍，是迄今确认的最轻双中子星组合。相关研究发表于《物理评论快报》。
中子星是大质量恒星在超新星爆发中死亡后留下的残骸。它们直径只有约二十公里，重量却可以超过太阳。其中一些会以极其规律的间隔发出射电信号，天文学家称它们为宇宙时钟。两颗中子星相互绕转构成的系统极难发现，目前已知的只有约三十个。
这类系统的价值在于它们最终的结局。当两颗星终于相遇时，会释放引力波，并产生金、铂等重元素。短轨道周期尤其珍贵，因为两颗星靠得更近，引力效应更强，并合也来得更早。在这个系统里，可见脉冲星的质量约为 1.30 倍太阳质量，伴星约为 1.19 倍，使这颗伴星跻身人类已知最轻的中子星之列。
极其紧密的轨道也为科学家提供了一间天然实验室。他们观测到多项爱因斯坦预言的效应：椭圆轨道缓慢转动，逃离强引力的光被拉向更红的颜色，时间流逝得稍稍更慢，而随着引力波带走能量，轨道本身也在收缩。测得的收缩速率与理论高度吻合。这个系统还可能帮助天文学家探测参考系拖拽效应——即自转的星体带动周围时空一同转动。
天文学家认为，这两颗星将在约 8200 万年后并合，最终很可能形成一颗质量更大的中子星。FAST 迄今已发现约 900 颗新脉冲星，而每一个像这样特殊的天体系统，都为我们理解物质本质以及宇宙中最重元素的来源补上一块拼图。