首页
登录
职称英语
The earliest known galaxies in the universe, which formed during the universe
The earliest known galaxies in the universe, which formed during the universe
游客
2023-09-09
11
管理
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. [br] 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://tihaiku.com/zcyy/2999225.html
相关试题推荐
Eitherentitlementprogrammes,______(如老年人的医疗和养老金制度),mustbereformed,ortaxe
[originaltext]W:Willyoutakethesebookstothelibraryduringyourlunchhou
[originaltext]W:Willyoutakethesebookstothelibraryduringyourlunchhou
[originaltext]W:Willyoutakethesebookstothelibraryduringyourlunchhou
[originaltext]W:Willyoutakethesebookstothelibraryduringyourlunchhou
Duringthatterriblefaminealotofpeoplehad_____________(没有选择,只能吃草和树叶).no
What’syourearliestchildhoodmemory?Canyourememberlearningtowalk?Or
What’syourearliestchildhoodmemory?Canyourememberlearningtowalk?Or
What’syourearliestchildhoodmemory?Canyourememberlearningtowalk?Or
What’syourearliestchildhoodmemory?Canyourememberlearningtowalk?Or
随机试题
TheotherdayIannouncedthatIwouldgoabroadforfurtherstudiesrighta
代谢性酸中毒的发生是A:由于体内H2CO3增高所致 B:体内HCO3-减少所致
检验检测机构在质量体系运行中应做到()。A.检验检测机构的负责人要重视质量体系
教学过程是在理解、拿握已有文化科学知识基础上促进学生全面成长。这种观点属于()A
根据《证券公司监督管理条例》,证券公司未按照规定与客户签订业务合同,中国证监会可
李女士的女儿今年9月进入大学读书,孩子入学之际,她已经为孩子积累了15万元的教育
Thechangeinthatvillagewasmiraculou
2017年上半年,全国居民人均可支配收入12932元,比上年同期名义增长8.8%
个人抵押授信贷款提供了一个有明确授信额度的循环信贷账户,借款人可使用部分或全部额
境内单位经常项目外汇账户的限额统一用欧元核定。()
最新回复
(
0
)