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
72
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.
According to the discoveries of the astronomers, when did galaxies form?
选项
答案
Just 700 million years after the birth of the universe.
解析
根据题干中的关键词discoveries和form定位到文章第二段,可知发现表明,星系形成于宇宙诞生七千万年以后,再结合上一段可知,这些发现是天文学家得出的。
转载请注明原文地址:https://kaotiyun.com/show/957K777K
0
大学英语六级
相关试题推荐
Afewyearsagoitwasfashionabletospeakofagenerationgap,adivisionbetweenyoungpeopleandtheirelders.Parents【B1】__
A、He’sunabletoappearincourt.B、Hewisheshecouldbeabetterstudent.C、Heplaystennisbetterthanshedoes,D、He’snots
WithChina’srapideconomicdevelopments,environmentaldamagehasbecomeapressingissueinsociety.Itcallsforeffortsnot
A、Itallowsthemtomeetstudentsfromotheruniversities.B、Itpromotestheconceptofself-learning.C、Itallowsmoreflexibil
A、Becauseoftheincreaseofeconomy.B、Becausetheschoolshavetobuildmorebuildingsl.C、Mainlybecausetheexpenditureone
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
A、Bossandsecretary.B、Customerandsalesman.C、Doctorandpatient.D、Husbandandwife.B
OrganicFoodOrganicfarmingwasamongthefastestgrowingsegmentsofU.S.agricultureduringthe1990s.Thevalueofretai
A、Itsufferedfromtoothache.B、Itfell32floorsanddied.C、Itmagicallysurvivedfallingfromhighbuilding.D、itwaspushed
A、Itisasmallamounttopayforsomuchpreciousmetal.B、Itisdifficulttojudgethevalueofsuchanobject.C、Itisreason
随机试题
有人认为:“没有杀人的目的,就不构成故意杀人罪。”请运用相关刑法理论和规定进行辨析。
情志抑郁两胁胀痛,其病机多属不耐疲劳乏力肢困,其病机多属
患儿,3个月。易激惹,烦躁多哭,夜寐不安,多汗,摇头擦枕,生长发育与同龄儿相同。X线骨骼检查正常。实验室检查:血清总钙及血磷偏低,钙磷乘积36,碱性磷酸酶稍有增高。初步诊断为维生素D缺乏性佝偻病,其分期是
甲公司以其机器设备为乙公司设立了质权。10日后,丙公司向银行贷款100万元,甲公司将机器设备又抵押给银行,担保其中40万元贷款,但未办理抵押登记。同时,丙公司将自有房产抵押给银行,担保其余60万元贷款.办理了抵押登记。20日后,甲将机器设备再抵押给丁公司.
以下选项中关于基坑基底稳定控制方法说法正确的是()。
申报日期栏应填______。征免栏应填______。
成年子女对父母的赡养是无条件的,有负担能力的子女都应当履行赡养义务,下列选项不属于赡养义务的承担主体()。
游客要求单独用餐时,导游可以协助安排,但须告知餐费须游客自理,且未享受的综合服务费不退。()
在教育研究中,访谈法与问卷法相比()
Chinahasoutlinedanewapproachtoforeigninvestment,withplannerssayingtheywillnowfocuslessonattractinglargeamoun
最新回复
(
0
)