In contrast, theoretical astronomers create and investigate models of things that cannot be observed.
ɪn kˈɑːntɹæst, θiəɹˈɛɾɪkəl ɐstɹˈɑːnəmɚz kɹiːˈeɪt ænd ɪnvˈɛstᵻɡˌeɪt mˈɑːdəlz ʌv θˈɪŋz ðæt kænˈɑːt biː əbzˈɜːvd.