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
The earliest known galaxies in the universe, which formed during the universe’s "dark age" nearly 13 billion years ago, have bee
The earliest known galaxies in the universe, which formed during the universe’s "dark age" nearly 13 billion years ago, have bee
admin
2010-08-21
61
问题
The earliest known galaxies in the universe, which formed during the universe’s "dark age" nearly 13 billion years ago, have been spied by two teams of astronomers.
The discoveries, reported separately in this week’s issue of the journal Nature. suggest that galaxies were forming just 700 million years after the birth of the universe.
Theory holds that the universe formed 13.7 billion years ago when an extremely dense concentration of mass rapidly expended in an event known as the big bang.
The universe has been expanding ever since, so astronomers are able to age galaxies by computing how much. the wavelength of their light has stretched—or redshifted—as the expansion takes the galaxies farther from Earth. The redder the light is, the older and more distant the galaxy is.
The detection of such ancient galaxies adds intrigue (神秘色彩) to theories of how the very first galaxies formed, according to astronomers.
Were there many large, young galaxies in the early universe that are obscured from astronomers’ view by abundant gases absorbing their light? Or were galaxies rare and small way back then, as a prevailing theory suggests, and later clumped together to form larger galaxies such as the Milky Way?
"We believe that we need both these processes to explain what we see." Masanori lye, a professor at the National Astronomical Observatory of Japan. said in an email.
The galaxy, called IOK-1, formed about 750 million years after the big bang--60 million years closer to the event than the previous record holder.
Given the number of galaxies found during a later epoch about 810 million years ago, the researchers had expected to find as many as six galaxies like IOK-1 But the comparative rarity(稀有) of objects like IOK-l means that the universe must have changed significantly over the 60 million years that separate the two epochs, the team suggests.
lye and colleagues believe that they are witnessing the last phase of a process known as reionization(再次电离).
According to Iye, about 380,000 years after the fiery hot big bang, the universe cooled so much that protons and electrons recombined to form neutral hydrogen. This is known as the beginning of the dark age of the universe, because neutral hydrogen absorbs the light from stars.
As more galaxies started to form about 300 million years later, the hot stars heated the intergalactic (银河间的) medium and gradually reionized the neutral hydrogen back m protons and electrons. The ionized hydrogen then became more transparent, allowing the galaxies’ light to pass through
lye said the new results support the idea that neutral hydrogen was still abundant 750 million years after the big bang, blocking even older galaxies from view. "We are starting to see the last phase of cosmic reionization, or the dawn of the cosmic dark age," he said.
lye added that the discovery also supports the "hierarchical" theory of galaxy formation, which suggests that big, bright galaxies formed as smaller galaxies collided and merged. "The epoch we have probed is yet in this critical stage," he said.
The comparative rarity of IOK-1 means that significant changes must have occurred in the universe, over the 60 million years that ______.
选项
答案
separate the two epochs
解析
根据题干中的关键词comparative rarity 和60 million years定位到倒数第六段,可知诸如IOK-1之类物体相对的稀有性表明,在分割两个时代的六千万年间,宇宙一定有了重要的改变。
转载请注明原文地址:https://kaotiyun.com/show/657K777K
0
大学英语六级
相关试题推荐
TheCarnegieFoundationreportsaysthatmanycollegeshavetriedtobe"allthingstoallpeople".Indoingso,theyhaveincre
WithChina’srapideconomicdevelopments,environmentaldamagehasbecomeapressingissueinsociety.Itcallsforeffortsnot
A、Itwasadinnerparty.B、Itwasaneighborhoodparty.C、Itwasabirthdayparty.D、Itwasabankparty.A细节推断题。Rose意识到了自己的错误,“
A、ToreadthebookbythefamousBritishwriter.B、Tocovertheireyesduringaperiodofintensivereading,C、Tovisitdoctors
A、Itisclosetotheschool.B、Itischeap.C、Ithasconvenientfacilities.D、Thetenantagreementisgood.C推理判断题。题目问女士关于海怪暗示了什
A、Food.B、Theh’car.C、Money.D、Jack’seducation.C关键词理解题。男士说:“一年我们共赚5万美元,你都花到什么地方了?你不想给杰克攒大学学费了吗?”女士说:“我都花到什么地方了?难道你一天不吃三顿饭吗?”所
Childrenare【C1】______seriousillnessesbecauseoftheirparentssmokingathome,saysthegovernment’schiefmedicalofficer,
A、Countingsheep.B、Taking:sleepingpills.C、Drinkingcoffee.D、Drinkingmilk.A细节题。问的是对话中所提到的帮助睡眠的老方法,尽管答案都用来帮助睡眠,但是文章中只提到了一种
Thetendencynowadaystowanderinwildernessesisdelightfultosee.Thousandsoftired,nerve-shaking,over-civilizedpeoplea
Thetendencynowadaystowanderinwildernessesisdelightfultosee.Thousandsoftired,nerve-shaking,over-civilizedpeoplea
随机试题
行政监督检查
They’ve______us$,forthehouseShallwetakeit?
左心衰时呼吸困难的主要机制是
A.C1~3B.C4C.C5D.C6E.C7支配三角肌的是
党政机关在大众传媒上发布公文属于()。
下列关于刑事案件证据确实、充分的说法有误的是()。
()指自变量与因变量因果关系的真实程度,即研究结果的可精确解释程度。
Iftheonlineserviceisfreethenyouaretheproduct,technicianssay.GoogleandFacebookmakea【C1】______collectingpersonal
TheHomeOfficehasbeenthreatenedwithlegalactionamidclaimsitmadewhichmistakenlyimpliedthat22collegeswereboguso
A、Thecoach.B、Thecaptain.C、Aformerplayer.D、Abasketballfan.C①选项都是有关人物的身份,听音时注意人物的相关信息。②男士告诉女士球队的队员即将有新队服了,女士问为什么,男士告知是该球
最新回复
(
0
)