Sydney Institute for Astronomy (SIfA)

The Sydney Institute for Astronomy (SIfA) in the School of Physics at the University of Sydney was formed in 1991 to bring together three research groups:

- the Chatterton Astronomy Department
- the Astrophysics Department, and
- the Research Centre for Theoretical Astrophysics (RCfTA)

The Chatterton Astronomy Department was founded in 1961 to commission and operate the Narrabri Stellar Intensity Interferometer (1963-1976). The instrument's prime achievements were the first angular diameter measurements of main sequence stars and a demonstration of the power of combining interferometric and spectroscopic data to determine fundamental stellar properties. A total of 32 angular diameters of stars were measured and the temperature scale for early type stars is based on these measurements. The development of a next generation stellar interferometer was commenced in the mid-1970s with a prototype modern Michelson interferometer, leading to the development of the Sydney University Stellar Interferometer (SUSI), opened in 1991.

The Astrophysics Department was formed in 1962 to build the Molonglo Radio Observatory - a Mills Cross-type telescope with arms one mile (1.6km) long. Following the official opening in November 1965, the telescope began a program to map the entire accessible sky at a frequency of 408 MHz. This project was completed in 1978 and the Molonglo Reference Catalogue of 12000 sources was published in 1980. By mid-1981 the east-west arm of the Cross had been converted to the MOST (Molonglo Observatory Synthesis Telescope) which operated at the higher frequency of 843 MHz. After many successful targeted programs through the 1980s and early 90s, the MOST underwent a wide-field conversion to enable it to conduct a very sensitive survey of the southern radio sky over the period 1997 to 2006. The results of this conversion were SUMSS (Sydney University Molonglo Sky Survey) and MGPS (Molonglo Galactic Plane Survey), with several hundred thousand sources catalogued.

MOST was turned off in June 2023.

The Research Centre for Theoretical Astrophysics (RCfTA) was formed formed in 1991 as an Australian Research Council (ARC) Special Research Centre and was funded by the ARC for nine years up to 1999. The RCfTA had the particular aim to foster close links between theoretical and observational astrophysicists nationally and internationally by such means as visitor programs, workshops, collaborative research projects and joint appointments. A record of RCfTA activities and research can be found in its Annual Reports.

More recently SIfA has attracted new staff bring research interests ranging beyond the older departmental boundaries. These include several staff affiliated with the Complex Systems group in the School of Physics.

SIfA research spans a large range range of theoretical, observational and instrumental programs.