Dee ihe ga-aga n'ihu na paragraf a - N'oge na-adịghị anya, achọpụtara Cepheids na ụyọkọ kpakpando ndị ọzọ, dị ka Andromeda (ọkachasị site n'aka Edwin Hubble na 1923<unk>24), ha wee bụrụ akụkụ dị mkpa nke ihe akaebe na "spiral nebulae" bụ ụyọkọ kpakpando nọọrọ onwe ha dị anya na Milky Way nke anyị. Ya mere, nchọpụta Leavitt ga-agbanwe echiche anyị banyere eluigwe na ala ruo mgbe ebighị ebi, ebe ọ kpaliri Harlow Shapley ịkwaga Sun anyị site n'etiti etiti ụyọkọ kpakpando ahụ na "Nkwurịta Okwu Ukwu
" na Edwin Hubble iji mee ka ụyọkọ kpakpando anyị pụọ n'etiti eluigwe na ala.