Halka 1920 Heber Doust Curtis iyo Harlow Shapley ay ka qayb qaateen dooddii weynaa
Dabeecadaha Nebula iyo Galaxy-yada iyo baaxada caalamka. Shapley waxa uu aaminsanaa in Nebulae-yada fog ay aad u yaryihiin isla markaana ay ku yaalaan gudaha galaxy-da Milky Way. Curtis wuxuu taageeray aragtida hadda la aqbalo ee ah in nebulae-yada ay ka fog yihiin, sidaas darteedna ay jiraan meerayaal kale oo aan ahayn Milky Way.