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
36
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.
What happened when the ionized hydrogen became more transparent?
选项
答案
The galaxies’ light can pass through.
解析
根据题干中的关键词ionized hydrogen和more transparent定位到倒数第三段最后一句,可知电离氢变得更为透明,这使得星系的光线可以从中穿过。
转载请注明原文地址:https://kaotiyun.com/show/B57K777K
0
大学英语六级
相关试题推荐
WithChina’srapideconomicdevelopments,environmentaldamagehasbecomeapressingissueinsociety.Itcallsforeffortsnot
A、Studentsarenotrequiredtoattendregularclasslectures.B、Theprofessorvideotapesclasslecturesforreview.C、Classesar
A、Shelosthercar.B、Shelostherbag.C、Shelostherkeys.D、Shelostherway.C该题问“女士发生了什么事”。男上说:“仔细想想,你一定把它丢在什么地方了?”女士说:“我不能
Obesity(肥胖)hasbecomeanepidemic.NotonlydoesObesityhavemore【C1】______healthconsequencesthansmoking,drinking,orpo
Itisanage-old【B1】______:MenarefromMars;WomenarefromVenus.Malesandfemalesshowdifferentbehaviorsalmostfrom【B2】
A、Theyareusuallymoreclever.B、Theygettiredeasily.C、Theyaremorelikelytomakeminormentalerrors.D、Theyaremoreski
A、Theblackone.B、Thewhiteone.C、Thebigone.D、Theonewithabiggeryard.D男士说“昨天我们看的那两座房子你喜欢哪一座?“女士:说“我觉得那座白色的房子漂亮些,但是那座砖房
Childrenare【C1】______seriousillnessesbecauseoftheirparentssmokingathome,saysthegovernment’schiefmedicalofficer,
A、Fiftypercenthigherthanthatofthenon-studentsofthesameage.B、One-quarterofthatofthenon-studentsofthesameag
随机试题
李煜《浪淘沙.帘外雨潺潺》:流水落花春去也,_______。
Everymorning,kidsfromalocalhighschoolareworkinghard.Theyaremakingandsellingspecialcoffeeatacoffeecafe.They
A.拒食致饿死B.食欲大增致肥胖C.出现假怒现象D.变得温顺驯服
下列哪种类型药物易从乳汁中分泌
1998年2月1日,甲与乙订立一份借款合同,约定甲借给乙5万元,乙于2000年4月至6月间还款付息。丙与甲订立一份保证合同,约定丙对乙履行债务承担保证责任。如果约定丙承担一般保证责任,保证期间为1998年2月15日至2000年6月30日。则依法律规定,
《刑法》第二百六十九条对转化型抢劫作出了规定,下列哪些选项不能适用该规定?()
在订立合同时显失公平的合同属于可变更、可撤销的合同,则其在法律上的特点有()。
Whenstudentsareaskedtofindoutthechangesoftheirhometownandmakeaplanforanexhibition,whichtypeofthefollowing
汽车安全气囊内所装的化学物质,能在碰撞互殴10毫秒内生产一种空气中含量最多的气体,该气体是氮气。()
在双向循环链表中,在P指针所指向的结点前插入一个指针q所指向的新结点,其修改指针的操作是(55)。
最新回复
(
0
)