VOA科学技术2024--Study of 'Twin' Stars Suggests Many Planets Might Be Exiles

Study of 'Twin' Stars Suggests Many Planets Might Be Exiles

　　A new study involving stars that formed together shows how lucky Earth is to be in a normal planetary system.

　　Researchers studied 91 pairs of stars that formed together and were similar in size and substance. Their research showed that a surprising number showed signs of having absorbed a planet.

　　The stars likely absorbed a planet after it was pushed out of a stable orbit. This might have been caused by gravitational influences from other planets or even other stars.

　　The stars involved are being called "twins" because they formed together. The researchers call them "co-natal stars," and they had equal masses and ages.

　　These "twins" were moving in the same direction in the Milky¹ Way galaxy² but were not connected by gravity.

　　Researchers chose the twin stars because a star's chemistry likely changes when it absorbs a planet. The planet would introduce amounts of a few elements that are not present in a normal star.

　　The researchers looked for stars that were different from their twin. They also tried to identify elements in the stars that would show that a planet had been absorbed. Those elements include iron, nickel, or titanium.

　　In at least seven of the twin stars, one of the two stars showed signs of absorbing a planet.

　　Fan Liu of Monash University in Australia was the lead writer of the research that was released in the publication Nature.

　　Scientist Yuan-Sen Ting of the Australian National University and The Ohio State University helped write the study. He commented that the research really shows what a lucky position Earth is in. He said, "The stability of a planetary system like the solar system is not a given."

　　The researchers used the European Space Agency's Gaia space observatory³ to find the twin stars. They also used telescopes in Chile and Hawaii to identify the chemical elements present in the stars.

　　The stars were as close as 70 light years from Earth and as far as 960 light years away. A light year is the distance light travels in a year, or 9.5 trillion kilometers.

　　The researchers said it is most likely that their observations showed that whole planets had been absorbed. But they added it was possible they were identifying planetary building blocks being absorbed during a system's period of planet formation.

　　Some stars like our sun expand towards the end of their life. During this time, they might absorb nearby planets. Later, the stars collapse⁴ becoming very small, dense⁵ stars called white dwarves⁶. Ting said all stars like the sun become much larger. Ting said Earth will be absorbed by the sun.

　　The stars in the study were not nearing the end of their life.

　　Instability in planetary systems might be more common than once thought. About eight percent of the twin stars studied had one star that likely absorbed a planet.

　　Ting said most planetary systems, like our solar system, should be stable. He said the reason is that planets are mostly influenced by their main star, not other planets in their system.

　　Ting added that for other planetary systems with different beginnings and conditions, this might break down. That might lead to instability.

　　Ting said the study shows that many planetary systems are unstable⁷. That means there are always planets thrown into or out of these systems.

　　Since only a small percentage of these planets are absorbed, there might be more planets than once thought traveling in exile without a star to orbit.

　　Ting said, "Understanding which planetary systems are stable or not is a long-time goal of planetary dynamics⁸ theorists."

　　Words in This Story

　　pair –n. two of something

　　absorb – v. to take in (something, such as a liquid) in a natural or gradual way

　　stable – adj. in a good state or condition that is not easily changed or likely to change

　　galaxy – n. any one of the very large groups of stars that make up the universe

　　solar system – n. our sun and the planets that move around it

　　dynamics – n. the science that studies motion and the forces that cause or stop motion

1 milky   

adj.牛奶的，多奶的；乳白色的

参考例句：

• Alexander always has milky coffee at lunchtime.亚历山大总是在午餐时喝掺奶的咖啡。
• I like a hot milky drink at bedtime.我喜欢睡前喝杯热奶饮料。

2 galaxy   

n.星系；银河系；一群(杰出或著名的人物)

参考例句：

• The earth is one of the planets in the Galaxy.地球是银河系中的星球之一。
• The company has a galaxy of talent.该公司拥有一批优秀的人才。

3 observatory   

n.天文台，气象台，瞭望台，观测台

参考例句：

• Guy's house was close to the observatory.盖伊的房子离天文台很近。
• Officials from Greenwich Observatory have the clock checked twice a day.格林威治天文台的职员们每天对大钟检查两次。

4 collapse   

vi.累倒；昏倒；倒塌；塌陷

参考例句：

• The country's economy is on the verge of collapse.国家的经济已到了崩溃的边缘。
• The engineer made a complete diagnosis of the bridge's collapse.工程师对桥的倒塌做了一次彻底的调查分析。

5 dense   

a.密集的，稠密的，浓密的；密度大的

参考例句：

• The general ambushed his troops in the dense woods. 将军把部队埋伏在浓密的树林里。
• The path was completely covered by the dense foliage. 小路被树叶厚厚地盖了一层。

6 dwarves   

n.矮子( dwarf的名词复数 )；有魔法的小矮人

参考例句：

• Everyone will try to claim it: Men, Dwarves, wizards. 每个种族都会争取它的拥有权：人类，矮人，巫师。 来自电影对白
• Have you learned nothing of the stubbornness of Dwarves? 难道你还不了解那个矮人的倔强吗？ 来自电影对白

7 unstable   

adj.不稳定的，易变的

参考例句：

• This bookcase is too unstable to hold so many books.这书橱很不结实，装不了这么多书。
• The patient's condition was unstable.那患者的病情不稳定。

8 dynamics   

n.力学，动力学，动力，原动力；动态

参考例句：

• In order to succeed,you must master complicated knowledge of dynamics.要取得胜利，你必须掌握很复杂的动力学知识。
• Dynamics is a discipline that cannot be mastered without extensive practice.动力学是一门不做大量习题就不能掌握的学科。