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
26
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 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 Iye, 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 stared 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.
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 over 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/rQz7777K
0
大学英语六级
相关试题推荐
Wateristasteless,odorless,andnearlycolorless(ithasaslighthintofblue).Itisa【C1】______thatisessentialtoallkn
PresidentCoolidge’sstatement,"ThebusinessofAmericaisbusiness",stillpointstoanimportanttruthtodaythatbusinessi
A、Attheairport.B、Atthetravelagency.C、Inthestudentcenter.D、Inarestaurant.C
A、Thelibraryisinthebusiestpartofthecity.B、Thelibraryhasgrassandtreesaroundit.C、TheroofoftheMainReadingRo
ThewritingoftheConstitutionoftheUnitedStatesisanactofsuchgeniusthatphilosophersstillwonderatitsaccomplishme
ThewritingoftheConstitutionoftheUnitedStatesisanactofsuchgeniusthatphilosophersstillwonderatitsaccomplishme
A、Shewantstogetpeopletoreadmore.B、Shesettledeveryproblembydiscussingwithherhusband.C、Sheisworriedaboutther
A、Ajournaltailcoat.B、Anessay.C、Poetry.D、Ashortstory.D
Creativityhasbeenconsideredintermsofprocess,productorpersonandhasbeendefinedastheinterpersonalandtheinterper
Tobetterunderstandthenegotiationpracticesofothercultures,itisimportantforustobeawareofthestandardnegotiation
随机试题
甲状腺手术时不慎将甲状旁腺切除后会出现
砂炒后便于除去绒毛的药材是
背景南方电子电气有限公司(建设单位)新建液晶屏(LCD)生产车间,其生产线由建设单位从国外订购,A施工单位承包安装。A施工单位进场时,生产车间的土建工程和机电配套工程(B施工单位承建)已基本完工。A施工单位按合同工期要求,与建设单位、生产线供应商
建没工程项目的信息不包括( )。
保险标的物发生部分损失,投保人终止保险合同的,应当在保险人赔偿保险标的损失后的( )日内提出,超过这个期间,投保人不能再请求终止保险合同。
某民政局工作人员冯某利用职务便利挪用救济金2万元进行营利活动。冯某的行为构成何种犯罪?()
已知向量a=(x1,y1),b=(x2,y2),则下列说法错误的是().
据中国海关提供进出口统计数据显示:2011年12月份,乘用车出口3.7万辆,比上月下降了9.34%,比去年同期增长了30.53%;创汇金额2.93亿美元,比去年同期增长了45.22%。其中:小轿车产品出口3.24万辆,比上月下降了6.23%,比去
20世纪50年代中期,社会主义改造基本完成.标志着()(2009年多选)
Everyonedoestheirownthing,tothepointwhereafifth-gradeteachercan’t_________onafourth-gradeteacherhavingtaught
最新回复
(
0
)