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
41
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.
Why can astronomers age galaxies by computing how much the wavelength of their light has stretched?
选项
答案
Because the universe has been expanding ever since the big bang.
解析
根据题干中的关键词age galaxies和computing定位到第四段,可知宇宙自形成以来一直在扩张,因此天文学家可以通过计算星系中光线波长的延展度,来计算星系的年龄。
转载请注明原文地址:https://kaotiyun.com/show/n57K777K
0
大学英语六级
相关试题推荐
A、TheEnglishmen’shabits.B、TheEnglishmen’saccent.C、TheEnglishmen’scharacter.D、TheEnglishmen’steachingstyles,C考生要注意判断
A、Becauseshecannotfindahusbandforherself.B、Becausethefemalespiderislargerthanthemaleone.C、Becausethefemales
A、At7:30.B、At8:30.C、At9:00.D、At9:30.D时间计算题。首先,校车足从早上7:00开始每隔两小时开一班,星期六早上开车时间晚半个小时,即7:30开车。所以,星期六第二次班车应该是9:30开。
Childrenare【C1】______seriousillnessesbecauseoftheirparentssmokingathome,saysthegovernment’schiefmedicalofficer,
Childrenare【C1】______seriousillnessesbecauseoftheirparentssmokingathome,saysthegovernment’schiefmedicalofficer,
Firecanbethoughtofasanycombustionprocessintenseenoughtoemitlight.Itmaybeaquietlyburningflameorthebrillian
OrganicFoodOrganicfarmingwasamongthefastestgrowingsegmentsofU.S.agricultureduringthe1990s.Thevalueofretai
Withincreasingprosperity,WesternEuropeanyouthishavingaflingthatiscreatingdistinctiveconsumerandculturalpatterns
Wateristasteless,odorless,andnearlycolorless(ithasaslighthintofblue).Itisa【C1】______thatisessentialtoallkn
Shehasappliedtotheuniversity_____________(延长她对牛津大学的访问时间).
随机试题
在数字资源加工过程中,一本书如有多种版本,收集验证排版资源时应优先收集()。
高血压性脑梗死正确的是
女性患者,70岁,2个月心慌,下肢水肿,厌食,恶心,体重减轻8kg。既往:糖尿病2年,慢性支气管炎3年。体检:消瘦,轻喘,多汗,血压21/13kPa(160/100mmHg),甲状腺I度肿大,可闻血管杂音,双肺呼吸音清晰,心界稍向左扩大,心率128次/分,
某机电安装公司承包室外压力管道安装工程,干管直径DN350~DN450,管线长度4.5km。施工期多阴雨、工期紧。为保证工程质量,项目部把室外压力管道安装分为原材料检验、管架制作安装、管道预制、管道安装、管道焊接、管道试验、管道保温、管道吹扫等工序,按照质
根据企业破产法律制度的规定,人民法院作出的下列裁定中,当事人可以提出上诉的有()。(2006年)
对检验的记录和判定的结果进行签字确认的人员是________。
导游人员作为翻译身份赴宴要注意不要向客人祝酒,不要随意为客人夹菜。()修改:___________________________________
张老师将文房四宝装在一个有四层抽屉的柜子里,让学生猜笔、墨、纸、砚分别在哪一层。按照笔、墨、纸、砚的顺序,小李猜测四宝依次装在第一、二、三、四层,小王猜测四宝依次装在第一、第三、第四和第二层,小赵猜测四宝依次装在第四、第三、第一和第二层,而小杨猜测四宝依次
《拆彼墙建此墙》说明了什么问题?如何克服?
A.propertyB.runC.onA.allotherformsoftobacco【T7】________schoolgroundsB.ifthey’reonschool【T8】________C.smok
最新回复
(
0
)