ystystyst

Astimewenton,thehydrogenandheliumgasinthegalaxieswouldbreakupintosmallercloudsthatwouldcollapseundertheirowngravity.Asthesecontracted,andtheatomswithinthemcollidedwithoneanother,thetemperatureofthegaswouldincrease,untileventuallyitbecamehotenoughtostartnuclearfusionreactions.Thesewouldconvertthehydrogenintomorehelium,andtheheatgivenoffwouldraisethepressure,andsostopthecloudsfromcontractinganyfurther.Theywouldremainstableinthisstateforalongtimeasstarslikeoursun,burninghydrogenintoheliumandradiatingtheresultingenergyasheatandlight.Moremassivestarswouldneedtobehottertobalancetheirstrongergravitationalattraction,makingthenuclearfusionreactionsproceedsomuchmorerapidlythattheywoulduseuptheirhydrogeninaslittleasahundredmillionyears.Theywouldthencontractslightly,andastheyheatedupfurther,wouldstarttoconvertheliumintoheavierelementslikecarbonoroxygen.This,however,wouldnotreleasemuchmoreenergy,soacrisiswouldoccur,aswasdescribedinthechapteronblackholes.Whathappensnextisnot







































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