雅思听力材料-新行星的发现

雅思考试主要是通过对考生听、说、读、写四个方面英语能力的考核，综合测评考生的英语沟通运用能力，实现“沟通为本”的考试理念。对于雅思考生来说，也有很多考试难点和政策盲区需要帮助解答。今天雅思无忧网小编准备了雅思听力材料-新行星的发现，希望通过文章来解决雅思考生这方面的疑难问题，敬请关注。

　　在雅思听力备考中，大家想要提升听力水平，就需要做大量的听力练习。今天小编为大家准备的是雅思听力材料-新行星的发现，大家可以结合练习来积累这方面的场景知识，帮助我们在雅思听力考试中拿到一个不错的成绩。

　　If three's a crowd, a new planet recently discovered orbiting a sunlike star is really cluttering up its neighborhood.

　　The new planet is the fourth Jupiter-like world to be found around the young star HR 8799, astronomers announced today. The same team had previously found the other three planets in 2008, when they took a direct picture of the star system.

　　Of the more than 500 planets discovered to date outside our solar system, most have been found via indirect methods, such as looking for planets' gravitational tugs on their host stars or for dips in starlight when planets pass in front of their hosts.

　　The new planet was also found in a direct image of the HR 8799 system. But based on the masses of the planets and their distances from the star, the fourth world challenges current theories of planet formation, according to the study authors.

　　"This is the first multiplanet system directly imaged so far, so it's quite a feat," said lead study author Christian Marois, an astronomer at the Herzberg Institute of Astrophysics in Canada.

　　"But we are now stuck with four planets [and] we cannot explain their formation and their current locations by any of our models."

　　Fourth Planet Too Close to Its Parent?

　　The previously known planets around HR 8799 are about five, seven, and ten times Jupiter's mass. They orbit between 2.2 billion miles (3.5 billion kilometers) from the star—roughly the same as Neptune's distance from the sun—and 6.3 billion miles (10.1 billion kilometers), or almost twice Pluto's distance.

　　The most distant planet circles just inside a dusty disk similar to that produced by the solar system's Kuiper belt, a region of *all, icy bodies that includes Pluto.

　　The whole HR 8799 system is estimated to be no more than 60 million years old, so the planets are still glowing with heat from their formation. This heat signature is what betrayed the planets' positions in the previous infrared images of the star.

　　Astronomers found the fourth planet using the Keck II telescope on the peak of Mauna Kea in Hawaii. The instrument is equipped with a special near-infrared imager and adaptive optics to eliminate the blurring effect of Earth's atmosphere.

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