The Commonwealth Solar Observatory was established in January 1924, one of its purposes being the study of solar phenomena. By 1950 the Observatory's name had changed, becoming the Commonwealth Observatory. In 1957 the observatory located at Mount Stromlo became part of the Australian National University as the Department of Astronomy in the Research School of Physical Sciences.

The Department of Astronomy was established in the Research School of Physical Sciences when the Mount Stromlo Observatory became part of the Australian National University in 1957. It had since 1924 been the Commonwealth Solar Observatory. In 1946 when the Australian National University Act was passed, Richard Woolley was its director and, as a personal friend to Nugget Coombs, was well placed to argue for the inclusion of a department of astronomy and astrophysics at the fledgling university. Woolley met unexpected resistance from Mark Oliphant, the newly appointed director of the Research School of Physical Sciences who rejected the inclusion of the Observatory on the grounds of its continuing statutory responsibilities being incompatible with the structure and organisation of the school. As a compromise, Woolley would be appointed an Honorary Professor of Astronomy with the right to appoint a research fellow to his staff and supervise supervise research students, creating a de-facto Department of Astronomy. In 1954 the first Doctor of Philosophy degree awarded by the University was to one of these students, Antoni Przybylski. On Woolley's appointment as Astronomer Royal in 1955 the University administration agreed to incorporate the Observatory into the University and establish a Professor of Astronomy who would also act as its Director. The Mount Stromlo Observatory Act 1956 gave effect to this change and the observatory was renamed the Mount Stromlo Observatory and made a department within the research school. By 1962, the expanding Canberra population made it clear that a better site needed to be found. The decision was made to establish a permanent ‘field station’ rather than totally relocate the observatory. Siding Spring (near Coonabarabran) was officially opened on 5 April 1965. The department was renamed the Mount Stromlo and Siding Spring Observatories (MSSSO) and became an Institute of Advanced Studies centre in 1986. In 1998 it became the Research School of Astronomy and Astrophysics.