RR Lyrae
In 1961, Walter Baade and Henrietta H. Swope studied Draco Dwarf and discovered over 260 variables, of the 138 in the cluster's center, all but five were determined to be RR Lyrae. From this work a RR Lyrae derived distance modulus of 19.55 is found which implies a distance of 81 kpc.
Read more about this topic: Draco Dwarf