摘要
Likepeople,starsareborn.Theywillalsogrowoldanddie.Theirbirthplacesarehuge,coldcloudsofgasanddust,knownas“1)nebulas.”ThemostfamousoftheseistheOrionNebula.Itisjust2)visiblewiththeunaidedeye.Thesecloudsstartto3)shrinkundertheirown4)gravity.Asthecloudgetssmaller,itbreaksinto5)clumps.Eachclumpeventuallybecomessohotand6)densethatnuclearreactionsbegin.Whenthetemperaturereaches10milliondegreesCelsius,theclumpbecomesanewstar.
出版日期
2017年05月15日（中国期刊网平台首次上网日期，不代表论文的发表时间）
