Recent Study Gives New Information about Mysterious Planet

2023-11-20 16:18:40来源：网络

Recent Study Gives New Information about Mysterious Planet

最近的研究提供了关于神秘行星的新信息

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　　By John Russell

　　19 November 2023

　　Eris, a very small planet similar in size to Pluto, has remained a mystery since its discovery in 2005. The American spacy agency, NASA, explored Pluto in 2015 using its spacecraft New Horizons. Eris - about 40 percent farther from the sun - has never been visited.

　　But scientists are gaining a fuller understanding of Eris and its differences with Pluto. A recent study provides details about the little planet's structure and composition based on its relationship with its moon Dysnomia.

　　Eris, researchers said recently, appears to have a rocky inside under a level of ice. Pluto also has an icy outside with rock below, but has a higher ice content and is thought to have an underground liquid ocean.

　　"We already knew that Eris is more rock-rich than Pluto, but what we didn't know was whether Eris had separated the rock from the ice," said study lead writer Francis Nimmo of the University of California Santa Cruz. The study appeared in the publication Science Advances.

　　Nimmo said Eris got hot enough at some point in history to melt, and all the rock sank to the center.

　　"The ice is not motionless but is experiencing a slow churning motion, driven by leftover heat from the inside. Most likely there is no liquid ocean inside Eris," Nimmo said.

　　Eris has a diameter of about 2,326 kilometers. Pluto's is a little bigger at about 2,370 km. Both are smaller than the Earth's moon, which has a diameter of 3,475 kilometers. Because of the greater amount of rock, which is denser than ice, Eris has about 25 percent more mass than Pluto.

　　"As I like to think of it, take Pluto and add every single asteroid in the asteroid belt, and you get Eris," said study co-writer Mike Brown, one of the three scientists who discovered Eris.

　　Eris orbits at an average of about 68 times further from the sun than Earth. It completes a full turn around the sun in 557 years.

　　The moon, Dysnomia, is about 700 kilometers in diameter and made up mostly of ice.

　　"Just like the Earth-moon system, tides on Eris slowly push Dysnomia away and slow down the spin of Eris. This process has gone to completion: Eris and Dysnomia always present the same face to the other," Nimmo said.

　　Pluto has this same system with its moon Charon, while the Earth-moon system differs.

　　"The moon always presents the same face to the Earth, but the Earth does not return the favor," Nimmo said.

　　Eris and Pluto are located beyond Neptune, the outermost of our solar system's eight bigger planets. The International Astronomical Union, which sets definitions for planetary science, recognizes five very small planets known as dwarf planets - Ceres, Haumea and Makemake, in addition to Eris and Pluto. Eris is the most massive of them.

　　The new findings fill in some questions about Eris.

　　"Each of the largest dwarf planets is unique and we should be cautious about inferring too much from what we know about Pluto," Brown said.

　　I'm John Russell.

　　Will Dunham reported on this story for Reuters. John Russell adapted it for VOA Learning English.

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　　作者：约翰·罗素

　　2023年11月19日

　　自2005年被发现以来，冥王星大小相近的小行星厄里斯一直是个谜。美国航天局NASA在2015年使用其新视野号探测器探测了冥王星。而厄里斯 - 距离太阳的距离比冥王星远40% -从未被访问过。

　　但科学家们正在对厄里斯及其与冥王星的差异有更全面的了解。最近的一项研究根据厄里斯与其卫星迪斯诺米亚的关系，提供了关于这个小行星结构和组成的详细信息。

　　研究人员最近表示，厄里斯似乎在一层冰下面有一个岩石内部。冥王星也有一个冰冷的外部和下面的岩石，但冰的含量更高，且被认为有一个地下液态海洋。

　　"我们已经知道厄里斯比冥王星含有更多的岩石，但我们不知道的是厄里斯是否将岩石和冰分离开来，"加利福尼亚大学圣克鲁兹分校的研究主要作者弗朗西斯·尼莫说。这项研究发表在《科学进展》杂志上。

　　尼莫说，厄里斯在历史的某个时刻变得足够热，以至于融化，所有的岩石都沉到了中心。