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2018年雅思听力材料:新行星的发现

888真人赌博   2018-04-19   【

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文章摘要:2018年雅思听力材料:新行星的发现,此外,毫米波人体成像设备具有对人体无害、穿透力强的特点,其发射功率不及手机电磁波辐射的千分之一,能准确识别人体携带物品,有效提高检查的客观性、准确性、针对性,降低安检员的劳动强度,提升安检效率。能到省城去读书不仅是学生们的愿望,更是他和老师们殷切的期待。  ——澳门有多家主题各异的博物馆  澳门虽然地狭人稠,博物馆却不少,许多家主题各异的博物馆涵盖古今中外多个领域,展示澳门中外荟萃的多元文化。,目前,首创·美澜湾的设计标准、精装标准、施工工法已经成为全市保障房的样板和标杆。同时,销售使用节能低碳燃油,可以有效降低机动车燃油消耗及减少细颗粒物和氮氧化合物排放,对于治理雾霾、改善环境质量具有重大意义。高山茶产业种植、加工和流通环节等从业人员万多人,茶企等经营主体已成为丰顺农业发展的主力军,示范带动农户11000多户,未来将带动更多农户致富。。

2018年雅思听力材料:新行星的发现

  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 small, 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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