Buuxi weedha soo socota: Sanadkii 1917, Heber Curtis wuxuu arkay nova S Andromedae gudaha Nebula Great Andromeda (Messier object 31). Markii uu baaray sawirada waxa uu helay 11 kale oo cusub. Curtis waxa uu ogaaday in novahaasi ay celcelis ahaan 10 magnitudes ka yaryihiin kuwa ka soo baxa Milky Way. taasina waxay keentay in uu qiyaaso masaafada 150,000 oo parsecs. Waxa uu taageersan yahay aragtida ah "universes island", oo ah in nebula spiral ay yihiin galaxiyo madax banaan. Sanadkii 1920-kii
Dood weyn ayaa dhex martay Harlow Shapley iyo Heber Curtis, oo ku saabsan dabeecada Milky Way, Nebulae spiral, iyo cabirka Caalamka. Si uu u taageero sheegashadiisa ah in Nebula weyn ee Andromeda uu yahay galaxy dibadeed, Curtis wuxuu xusay muuqaalka wadooyinka mugdiga ah ee u eg daruuraha boodhka ee Wadada Caanaha, iyo sidoo kale wareejinta Doppler ee muhiimka ah.