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
2010-09-25
91
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 expanded 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 redshified-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 fast 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-1 means that the universe must have changed significantly over the 60 million years that separate the two epochs, the team suggests.
Iye 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 to protons and electrons. The ionized hydrogen then became more transparent, allowing the galaxies’ light to pass through.
Iye 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.
Iye 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/ZPz7777K
0
大学英语六级
相关试题推荐
We’veallusedthermometerstomeasuretemperaturebutsometimesweneedtomeasuretemperatureinplacesyoucan’tput
SometimesitappearsthateverytowninBritainhasatleasthalfadozenghosts.Ifitisn’tmurdervictims,thenit’sladiesi
TheWorldHealth【B1】______saysavianinfluenzacouldbecomeaworldwidethreatunlessgovernmentsactnowtostopit.Officials
Face-to-facecontactisbynomeanstheonlyformofcommunicationandduringthelasttwohundredyearstheartofmasscommuni
Televisionnowplayssuchanimportantpartinsomanypeople’slivesthatitis【B1】______forustotrytodecidewhetheritis
A、Itwillbeconsumedbymoreandmoreyoungpeople.B、Itwillbecomethefirstcourseatdinnerparties.C、Itwillhavetobec
Nosooner________________(我一出门,就认识到错了).
Povertyexistsbecauseoursocietyisanunequalone,andtherearepowerfulpoliticalpressurestokeepitthatway.Anyattemp
A、Theydeveloptheiridentitieswithinpeergroups.B、Theyreceiveinformaleducation.C、Theyperformvoluntarycommunityservic
Japanesefirmshaveachievedthehighestlevelsofmanufacturingefficiencyintheworldautomobileindustry.Someobserversof
随机试题
在急性蜂窝织炎中,浸润的炎细胞主要是:
具有催化作用的小RNA称为
有关人禽流感的预防,以下错误的是
夏某,男,32岁。因结肠肿瘤住院手术,整日愁眉不展、不思饮食,为了对病人进行有针对性的心理护理,护士交谈前,不需要收集的资料是
A.急性胎儿窘迫B.轻度新生儿窒息C.慢性胎儿窘迫D.重度新生儿窒息E.新生儿产伤胎儿娩出后1分钟,心跳规则有力,呼吸表浅不规则,Apgaur评分为4~7分,诊断为
下列明细分类账,应采用横线登记式账页格式的是( )。
可转换公司债券发行人设置()的,应明确约定实施这些条款的条件、方式和程序等。
甲企业是一家处于成长期的健身公司,地处高校密集的大学城。公司实行会员制,顾客主要通过电话和网络预约方式来门店进行健身。甲企业决定采用平衡计分卡进行绩效管理,从顾客的角度考虑,其平衡计分卡的内容包括()。
某市一家洗衣机生产企业为增值税—般纳税人,适用25%的企业所得税税率。2012年生产经营业务如下:(1)3月,企业将自产的一批洗衣机换取甲公司(增值税一般纳税人)生产的原材料,洗衣机的不含税市场价格为300万元,成本210万元,企业已做销售账务处
十进制数5的单精度浮点数IEEE754代码为()。
最新回复
(
0
)