Tinsley's work was on the development of these galaxies and of the stars within.
She asked 'how did they form?' Tinsley created models of galactic formation that were said to be more realistic than other models at the time, combining a detailed understanding of stellar evolution with knowledge of the motions of stars and nuclear physics. In short, Tinsley married together many branches of knowledge and created a workable model of galactic creation. Her work had profound effects on the study of astrophysics at the time, changing the direction of thinking on galactic formation.
Tinsley herself went on to become the professor of Astrophysics at Yale University in 1978, but unfortunately she was diagnosed with cancer the same year, and passed away 3 years later, although she continued to work right up until her death. Throughout her life Tinsley authored over 100 scientific papers, and was heralded as a great scientist, teacher and an inspiration to women scientists both in America and New Zealand.