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
Supernovae are massive exploding giant stars. A supernova is known as one of the most energetic explosive events. When the expl
Supernovae are massive exploding giant stars. A supernova is known as one of the most energetic explosive events. When the expl
admin
2010-07-19
18
问题
Supernovae are massive exploding giant stars. A supernova is known as one of the most energetic explosive events. When the explosion occurs, the resulting illumination can be as bright as an entire galaxy. It occurs at the end of a star’s lifetime, when its nuclear fuel is exhausted and it is no longer supported by the release of nuclear energy. This will cause a blast wave that ejects the star’s envelope into interstellar space. The result of the collapse may be, in some cases, a rapidly rotating neutron star that can be observed many years later as a radio pulsar. As a result of gravitational forces acting against the nuclear structure of the core of a fuel depleted star, tremendous shock waves are generated, which causes the outside layers of the star to be blown away from the core.
Gravitational forces condensing hydrogen gas raises the temperature at the center of the star to the point where nuclear fusion is initiated. Hydrogen is fused into helium and energy is given off in the process. As more helium accumulates at the center, the temperature rises due to compression until another nuclear fusion is initiated. This time helium is converted into carbon and oxygen and additional energy is given off during the nuclear fusion.
A similar process continues with carbon and oxygen fusing to neon, magnesium and oxygen. These elements then undergo another fusion process as the temperature and pressure increase to produce silicon and sulfur. The latter two elements then fuse into iron.
During each nuclear fusion, energy is given off. However, nuclear fusion stops at iron because energy is no longer produced by fusion. The iron core collapses very quickly ( within hours or less). Since the iron core can collapse only so far and can no longer undergo fusion, it becomes extremely hot and now begins to expand rapidly. The expanding iron and the collapsing outer gases collide with each other producing tremendous shock waves which blow the outer layers away from the cure, thus causing the supernova’s gigantic explosion.
Which of the following causes the outside layer of the star to be blown away from the core?
选项
A、Shock waves.
B、The iron core collapse.
C、Blast wave.
D、The fusing of carbon and oxygen.
答案
A
解析
转载请注明原文地址:https://kaotiyun.com/show/zYlO777K
0
专业英语八级
相关试题推荐
TheReader’sDigestinvestigationaskedAmericanswhichwasthebiggestthreattothenation’sfuture--bigbusiness,biglaboro
A、ItsarrangementinthebilingualEnglish-Chineseformanditsdetailedexplanatorynotes.B、Itstasteforpeopleofallkinds
Thirty-twopeoplewatchedkittyGenovesebeingkilledrightbeneaththeirwindows.Shewastheirneighbor.Yetnoneofthe32he
Justas【1】______isfamousforthetango,soAmerican【1】______iswell-knownforjazz,atypicalAmericaninvention
LeavingHomeGenerallyforstudentsorforpeoplejustbeginningwork,therearepractical【1】_____of
A、PredominanceB、LocalcharacteristicsandcustomsC、IndividualidentityD、PotentialdividingforcesB
Thefamous_____GoldRushbeganintheU.S.inthemid-nineteencentury.
Atpresent-companiesandindustriesliketosponsorsportsevents.Tworeasonsareputforwardtoexplainthisphenomenon.Thef
Moderatedrinkingreducesstrokerisk,studyconfirms.Similartothewayadrinkortwoadayprotectsagainstheartattacks,m
Theysparkleandglitterinthelight.Nootherrocksaresohard.Theyareveryvaluable.Itmightcostthousandsandthousands
随机试题
下列为口服复方短效避孕药的妇女提供的健康指导内容,不正确的是
根据症状其治则是:最佳的方剂是:
A.麻醉药品B.一类精神药品C.二类精神药品D.医疗用毒性药品E.放射性药品每张处方不超过2日极量的药品是
白矾的主治病证是()硫黄的主治病证是()
理发业由很多中小企业组成。其中没有任何一家企业占有显著的市场份额或对整个产品的发展产生重大影响。造成理发业上述状况的原因有()。
如图2所示,半圆形玻璃砖置于光屏PQ的左下方,一束白光沿半径方向从A点射入玻璃砖,在O点发生反射和折射,折射光在光屏上呈现七色光带。若入射点由A向B缓慢移动,并保持白光沿半径方向入射到O点,观察到各色光在光屏上陆续消失。在光带未完全消失之前,反射光的强度变
给定材料材料1:媒体披露H省一中学发生群发性肺结核事件后,A县政府官网于2017年11月16日中午通报证实确有此事.但对事件涉及的范围和人数只字未提。而根据《结核病防治管理办法》,肺结核疫情严重,构成突发公共卫生事件的,应当及时向社会公
字符串"%%\"ABCDEF\"\\"的长度是()。
A一定B相信C久D爱好E检查F礼物例如:A:你有什么(D)?B:我喜欢体育。A:你对自己的成绩还满意吗?B:还可以,我()自己以后会跑得更快。
TheWindWasvery______yesterday.
最新回复
(
0
)