首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
外语
When the end of the world comes, we’ll know what to blame. Scientists have found compelling evidence that the Sun has a baby bro
When the end of the world comes, we’ll know what to blame. Scientists have found compelling evidence that the Sun has a baby bro
admin
2011-01-02
33
问题
When the end of the world comes, we’ll know what to blame. Scientists have found compelling evidence that the Sun has a baby brother, a dark star whose eccentric orbit is responsible for periodically showering the Earth with comets and meteorites.
The dark star — named Nemesis by astronomers — is thought to be a brown dwarf that spins round the Sun in an orbit so large it is measured in light years, the distance light travels in a year, equivalent to about 6,000 billion miles.
The research suggests that, every 26m years, the star’s eccentric orbit brings it within one light year of the solar system. There it causes havoc in the Oort Cloud, a huge region surrounding the solar system that contains billions of bits of cosmic rabble left over from the formation of planets.
Of the millions of rocks it throws out of orbit at each visit, some hurtle Earthwards, and have several times nearly wiped out life on Earth.
Astronomers have long wondered if the Sun has a smaller partner. Recently, two independent groups of researchers have found evidence of one.
One group, led by John Matese, professor of physics at the University of Louisiana at Lafayette, confirms the notion that it is most likely to be a brown dwarf, a star that never accumulated enough mass to ignite and which has simply sat in space smoldering for billions of years.
Matese studied 82 comets from the Oort Cloud and found common elements in the shape of their orbits that could only be explained if they had been influenced by the gravitational pull of an object several times the size of Jupiter and existing about 25,000 times farther from the Sun than tile Earth.
Matese said: "A companion to the Sun orbiting at these distances would have little effect on the planets. But it would play a big role in the way comets ’ made their way’ from their birth places in the planetary disc out to the Oort Cloud and in how they can return to the inner solar system."
Further research was published by Richard Muller, professor of physics at the University of California, Berkeley, following analyses of moon rock samples brought back to Earth by Apollo 14.
The absence of a protective atmosphere means the moon has been subjected to intense bombardment in its 4.5 billion-year existence.
Muller’s breakthrough was to find a way to date how long ago any particle was melted -- meaning he could build up a picture of whether the moon gets a constant barrage or suffers spells of intense bombardment.
He said, "The evidence clearly shows that the moon has gone through spells of relatively frequent impacts and others of reduced intensity. I believe it is likely that this is because the Oort Cloud is being disturbed by a massive body that is throwing comets out of stable orbits, a small fraction of which could reach the Earth."
Muller and others believe that the dark star probably takes about 26m years m complete an orbit around the sun.
Other scientists have already noted that mass extinctions of life on Earth seem to occur in a pattern with gaps equivalent to multiples of 26m, suggesting some regular event is causing the comets to come Earth’s way.
The best-known such event was the one that wiped out the dinosaurs 65m years ago, but that was not the worst; the planet has suffered several such large mass extinctions.
Astronomers have found the first Earth-sized planet orbiting another star. The discovery raises the chances of finding planets that could support life as we know it.
选项
答案
A
解析
细节题。倒数第四段提到,马勒和其他人认为Nemesis这颗暗星要用两千六百万年才能沿轨道绕太阳一周,所以A正确。倒数第五段提到,马勒认为Nemesis会影响到Oort Cloud,并非受其影响,故排除B;该段中Muller还提到Nemesis不断往轨道外扔彗星,但并没有说扔到了Oort Cloud里,故排除C;倒数第三段提到,其他科学家发现地球物种灭绝可能和Nemesis有关,可见该观点并非是Muller提出的,故排除D。
转载请注明原文地址:https://kaotiyun.com/show/07lO777K
0
专业英语八级
相关试题推荐
1 Iwillnowteach,offeringmywayoflifetowhomsoeverdesirestocommitsuicidebytheschemewhichhasenabledmetobeat
1 "Internationalcommunication"iscommunicationbetweenmembersofdifferentcultures.Thisdefinitionissimple.Butt
Beguninthelate1960sbyPentagonweaponsresearchersasasystemforeasingcommunica-tionbetweencomputersindisparateel
Thereisaperceptionabroadinthelandthat,becausesomesegmentsofthepublicaredissatisfiedwiththequalityofsomepar
TheValueofAnimalResearch Toparaphrase18th-centurystatesmanEdmundBurke,"allthatisneededforthetriumphof
1 Weoftenhearpeopleasksuchaquestion:Whydobadthingshappentogoodpeople?Theproblemis:Whatkindofpeoplearego
Achildwhohasoncebeenpleasedwithatalelikes,asarule,tohaveitretoldinidenticallythesamewords,butthisshould
"Home,sweethome"isaphrasethatexpressesanessentialattitudeintheUnitedStates.Whethertherealityoflifeinthefam
"Home,sweethome"isaphrasethatexpressesanessentialattitudeintheUnitedStates.Whethertherealityoflifeinthefam
ScotlandYard’stopfingerprintexpert,DetectiveChiefsuperintendentGeraldLamhournehadarequestfromtheBritishMuseum’s
随机试题
下列句中加横线的词语属于意动用法的是()
患者,女,24岁,人工流产术后1周,突然阴道出血增多,伴腹痛,无发热;查体:子宫稍大,质软,压痛,双侧附件区未扪及异常。该患者目前最应该进行的操作是
治疗抽动秽语综合征可选用的药物包括
A.处3年以下有期徒刑、拘役、管制或罚金B.处3年至7年有期徒刑,并处罚金C.处2年至7年有期徒刑,并处销售金额50%至2倍罚金D.处3年以上10年以下有期徒刑,并处罚金E.处3年以下有期徒刑、拘役管制或剥夺政治权利在自然灾害和突发事件
根据《污水综合排放标准》,属于第一类污染物的是()。
基坑在初期排水时,排水设备应选择()离心式水泵。
为了贯彻执行《中华人民共和国计量法》和《中华人民共和国强制检定的工作计量器具检定管理办法》,切实做好强制检定工作,某区人民政府批转区标准计量局提出了《关于强制检定的工作计量器具分期分批实施检定的报告的通知》。无论是强制检定,还是非强制检定,它们检定的依
当备选供货商有很大不同时,做出错误决策的概率很高,采购者一旦选错,会造成严重后果。
确定和调整最低工资标准应考虑的因素包括()
楚某1997年3月5日犯甲罪,追诉期限应为10年,2002年3月5日又犯乙罪,乙罪的追诉期限也是10年。这时甲罪的追诉期限应()。
最新回复
(
0
)