简介:1.IntroductionOneofthemostimportanttasksofmodernastronomyistoprobetheveryearlyuniverse.AccordingtothestandardBigBangtheory,primordialmatterconsistedofabout76%hydrogenand24%heliumbyweight,alongwithtracequantitiesofdeuteriumandlithium.Someofthisprimordialgaseventuallycooledenoughtocondenseintostars,andultimatelyformedgalaxies.Otherelements,suchascarbonandiron,areassumedtohavebeencreatedmuchlaterastheresultofstarformation.Theintergalacticmedium(IGM)islikelytocontainmorebaryonicmatterthanallthematter...