雅思免费课程NEW
剑桥题库机考HOT
雅思水平测试NEW
雅思选课中心
雅思听力
雅思口语
雅思阅读
雅思写作
雅思问答
雅思考试机经回忆
雅思动态NEW
雅思备考指导
雅思模拟题
雅思核心词汇NEW
雅思备考规划
扫码添加助教免费咨询雅思备考规划
扫码关注回复雅思获取最新雅思口语题库和备考资料
今天新东方在线小编给大家整理了雅思听力背景词汇盘点之新行星的发现,希望对大家的雅思听力考试提供帮助,更多雅思听力内容,欢迎随时关注新东方在线雅思网。
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.
Images from Keck II show that the newfound planet is also a gas giant, about seven times Jupiter's mass. But it orbits closer to the star, at a mere 1.4 billion miles (2.2 billion kilometers), equivalent to between the orbits of Saturn and Uranus.
The new Keck data also indicate there may be an asteroid belt just inside the newfound planet's orbit.
Widespread "Jupiters" Creating Dilemma
Overall, the HR 8799 system is starting to look like a scaled-up version of our solar system, the astronomers note. But the setup doesn't fit either of the two currently accepted models for how gas giant planets form, Marois said.
It's thought planets in general form out of the disks of gas and debris that surround many young stars. One model for how gas giants form is called gravitational instability, in which a perturbation in the disk causes a clump of material to suddenly coalesce into a gassy planet.
The other model is core accretion, in which material first clumps into a rocky core, and the core then gravitationally gathers nearby gases. (See "New Model of Jupiter's Core Ignites Planet Birth Debate.")
According to Marois's team, the problem with such widespread gas giants is that they all couldn't have formed the same way. Too far from the star and there's not enough gas for core accretion to work, but too close and it's too hot for debris to become gravitationally unstable.
"The system is either just too young and the planets are just too far away and don't have time to form before the gas in the disk is depleted, or they are too close and the disk is too warm to form planets," Marois said.
Gas giant planets have been found in orbits close to their parent stars, sometimes even closer than Mercury is to the sun. In these cases, many experts believe the so-called hot Jupiters may have formed farther away from their stars and then migrated closer over time.
"That is one possible way out in explaining the problem. There is probably more to it than that—but this will require more work," Marois said.
"But the fact that we are seeing this planetary system at this early stage of evolution is definitely giving us insight on what happened to arrive at its current configuration."
The HR 8799 planetary system is described in a paper published online this week by the journal Nature.
本文关键字: 雅思听力背景词汇
资料下载
雅思写作高频词汇PDF下载
发布时间:2023-08-26添加新东方在线雅思助教号
回复【200】获取
590组雅思阅读写作必背短语PDF版下载
发布时间:2023-08-09添加新东方在线雅思助教号
回复【590】获取
雅思学术词汇搭配表PDF版下载
发布时间:2023-08-04添加新东方在线雅思助教号
回复【ACL】获取
雅思口语part3结构策略PDF版下载
发布时间:2023-08-04添加新东方在线雅思助教号
回复【Part3】获取
雅思听力高频场景词PDF版下载
发布时间:2023-08-09添加新东方在线雅思助教号
回复【高频词】获取
雅思口语Part2答案示范15篇PDF下载
发布时间:2023-07-26添加新东方在线雅思助教号
回复【P2】获取
雅思小作文35组必备表达PDF下载
发布时间:2023-07-26添加新东方在线雅思助教号
回复【35】获取
雅思阅读高频短语PDF下载
发布时间:2023-07-20添加新东方在线雅思助教号
回复【短语】获取
200组雅思写作高频词汇PDF下载
发布时间:2023-07-20添加新东方在线雅思助教号
回复【200】获取
雅思写作话题词汇PDF下载
发布时间:2023-07-16添加新东方在线雅思助教号
回复【话题】获取
50组雅思口语同义替换词PDF下载
发布时间:2023-07-10添加新东方在线雅思助教号
回复【替换】获取
雅思写作大作文精选题目101PDF下载
发布时间:2023-07-09添加新东方在线雅思助教号
回复【101】获取
雅思口语核心300词PDF下载
发布时间:2023-06-23添加新东方在线雅思助教号
回复【300】获取
雅思阅读分类词汇PDF下载
发布时间:2023-06-17添加新东方在线雅思助教号
回复【分类词】获取
雅思口语必备习语PDF下载
发布时间:2023-06-17添加新东方在线雅思助教号
回复【习语】获取
雅思小作文常用词汇66词PDF下载
发布时间:2023-06-16添加新东方在线雅思助教号
回复【66】获取
雅思口语常见功能结构109句PDF下载
发布时间:2023-06-08添加新东方在线雅思助教号
回复【109】获取
10年雅思写作题库PDF下载
发布时间:2023-06-08添加新东方在线雅思助教号
回复【写作话题】获取
雅思图表作文精选套句50句PDF下载
发布时间:2023-05-28添加新东方在线雅思助教号
回复【50】获取
雅思写作99组高频词汇PDF资料
发布时间:2023-05-28添加新东方在线雅思助教号
回复【99】获取
2023年5月雅思口语新题题库PDF版本
发布时间:2023-05-14添加新东方在线雅思助教号
回复【新题】获取
2023年5-8月雅思口语新题题库与解析PDF版本
发布时间:2023-05-06关注新东方在线考雅课程中心服务号
回复【新题】获取
雅思听力考点词汇PDF资料
发布时间:2023-04-27添加新东方在线雅思助教号
回复【考点词】获取
雅思听力机经词汇PDF资料
发布时间:2023-04-24添加新东方在线雅思助教号
回复【TL】获取
雅思口语Part1常见话题语料库PDF资料
发布时间:2023-04-20添加新东方在线雅思助教号
回复【Part1】获取
剑桥雅思阅读长难句50句PDF资料
发布时间:2023-04-19添加新东方在线雅思助教号
回复【长难句】获取
雅思阅读核心学术词汇表PDF资料
发布时间:2023-04-07关注新东方在线考雅课程中心服务号
回复【核心】获取
100个雅思写作观点词和替换词表达PDF资料
发布时间:2023-03-24关注新东方在线考雅课程中心服务号
回复【100】获取
雅思阅读分类词汇PDF资料
发布时间:2023-03-22关注新东方在线考雅课程中心服务号
回复【分类词】获取
雅思阅读短语PDF资料
发布时间:2023-03-08关注新东方在线考雅课程中心服务号
回复【短语】获取
添加新东方在线雅思助教,
回复【口语】获取雅思口语资料大礼包
推荐阅读
更多>>大家日常在备考雅思听力的时候可以多注意一些易混词汇,新东方在线雅思为大家整理了雅思考试听力易混词汇,希望对大家的雅思备考有所帮助!
大家日常在备考雅思听力的时候可以多注意一些易混词汇,新东方在线雅思为大家整理了雅思考试听力易混词汇,希望对大家的雅思备考有所帮助!
大家日常在备考雅思听力的时候可以多注意一些易混词汇,新东方在线雅思为大家整理了雅思考试听力易混词汇,希望对大家的雅思备考有所帮助!
大家日常在备考雅思听力的时候可以多注意一些易混词汇,新东方在线雅思为大家整理了雅思考试听力易混词汇,希望对大家的雅思备考有所帮助!
为了帮助大家高效备考雅思,新东方在线雅思为大家整理了雅思听力技巧,希望对大家雅思备考有所帮助。
资料下载
更多>>添加新东方在线雅思助教号
回复【200】获取
添加新东方在线雅思助教号
回复【590】获取
添加新东方在线雅思助教号
回复【ACL】获取
添加新东方在线雅思助教号
回复【Part3】获取
添加新东方在线雅思助教号
回复【高频词】获取
添加新东方在线雅思助教号
回复【P2】获取
添加新东方在线雅思助教号
回复【35】获取
添加新东方在线雅思助教号
回复【短语】获取
添加新东方在线雅思助教号
回复【200】获取
添加新东方在线雅思助教号
回复【话题】获取
添加新东方在线雅思助教号
回复【替换】获取
添加新东方在线雅思助教号
回复【101】获取
添加新东方在线雅思助教号
回复【300】获取
添加新东方在线雅思助教号
回复【分类词】获取
添加新东方在线雅思助教号
回复【习语】获取
添加新东方在线雅思助教号
回复【66】获取
添加新东方在线雅思助教号
回复【109】获取
添加新东方在线雅思助教号
回复【写作话题】获取
添加新东方在线雅思助教号
回复【50】获取
添加新东方在线雅思助教号
回复【99】获取
添加新东方在线雅思助教号
回复【新题】获取
关注新东方在线考雅课程中心服务号
回复【新题】获取
添加新东方在线雅思助教号
回复【考点词】获取
添加新东方在线雅思助教号
回复【TL】获取
添加新东方在线雅思助教号
回复【Part1】获取
添加新东方在线雅思助教号
回复【长难句】获取
关注新东方在线考雅课程中心服务号
回复【核心】获取
关注新东方在线考雅课程中心服务号
回复【100】获取
关注新东方在线考雅课程中心服务号
回复【分类词】获取
关注新东方在线考雅课程中心服务号
回复【短语】获取
编辑推荐
雅思新题
阅读排行榜
相关内容