Mopra, the southern hemisphere’s largest millimetre-wave telescope

Mopra — Millimetre Wave Excellence
The 22m Mopra telescope near Coonabarabran is currently the largest single dish mm-wave telescope in the southern hemisphere and the fourth largest of its kind in the world. Thanks to a collaborative project between UNSW and CSIRO the facility was upgraded in 1999 from a 15m diameter millimetre telescope to a 22m millimetre telescope.

At the present time a number of other Southern Hemisphere telescopes are being planned and built around the world. The US National Radio Astronomy Observatory and the European Southern Observatory are in the last stages of planning ALMA, a large synthesis sub-mm/mm telescope to be completed in 2011 on the Atacama Plateau in Chile. Before then Australia has a window of opportunity as the only country in the southern hemisphere with a millimetre-capable interferometer – the Australia Telescope Compact Array. Mopra occupies a unique position, allowing molecular surveys of large portions of the southern sky from which interesting astronomical sources may then be selected for detailed investigation with the Compact Array.

Mopra was used to search for the biologically significant molecules propylene oxide and glycine in the interstellar medium. The detection of either of these molecules would be of great significance for the origin of life question because of the possible extraterrestrial origin for both primordial biological molecules and for the chiral imbalance found in both living systems and in meteorites. The Star Formation group at UNSW also swept the southern galactic plane for carbon monoxide, measuring the distance to known medium-mass star formation regions within 1 kiloparsec of the Sun. The goal is to correlate protostar properties (mass, density, temperature, bulk motions) with their luminosity (i.e., mass), covering the gap usually not addressed in studies of low- and high-mass star-forming regions.

The telescope has had its fair share of international visitors also. In collaboration with the University of Leeds, kinematic distances were measured towards a sample of mid-infrared sources discovered through the MSX satellite mission. Kinematic distances are crucial to determining the luminosity of the candidate protostars and identifying near-by low mass young stellar objects. This is essential if we are to understand massive star formation as a function of mass, age, environment and location. With the Center for Astrophysics in the USA we collaborated to use Mopra to test the idea that star formation occurs by coalescence by looking for any relative motions between star-forming condensations. Such condensations are expected to move with respect to the ambient material in this scenario, as they gravitate to the centre of a cluster where they can coalesce to form more massive stars.

Cormac Purcel



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