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The Square Kilometre Array

For the past ten years, astronomers from 10 countries have been contemplating the next big step forward in our understanding of the Universe. So far, our telescopes have probed back in time to a period when the Universe was about 1/10 of its current age. At that time, stars, planets and galaxies were already formed. To understand how these objects were formed, we need to look back to a time before there were stars and galaxies, when the Universe consisted of only a dark void of Hydrogen gas. In this cosmic Dark Age, the first stars formed and the first light shone in the Universe – the cosmic dawn. To capture this moment, we will need to build a telescope that can detect the weak signals coming from Hydrogen gas emitted at a time when the Universe was in the first 1% of its life. Such a telescope will have to work in the radio part of the spectrum and have a collecting area of around 1 million square metres, about 50 times larger than anything that exists today. This Square Kilometre Array (SKA) will also need receiving dishes spread out over distances of more than 3000 km to accurately capture the images of the first stars and galaxies.

The radio signals from the cosmic dawn will reach the Earth at a frequency in the FM part of the radio spectrum. This piece of the radio band is completely saturated with man-made signals over most of the Earth’s inhabited regions. To avoid this interference, the new telescope will have to be placed in a remote location, yet still be accessible to astronomers and engineers from around the world. An international search for such a location has shown that the Midwest of Western Australia is the most radio quiet region on Earth. The vast extent of the Australia continent also allows for the positioning of dishes over the thousands of kilometres needed to discovery the sources of the first light. The remote desert of WA, home to Aboriginal peoples who were arguably the world’s first astronomers, may provide mankind with its clearest view of the first objects created – the seeds of the Universe we see around us today.

The Murchison Radio-astronomy Observatory (MRO) is situated on a 350,000 hectare cattle and sheep station, 300 kilometres north east of Geraldton in the classical Australian landscape of flat red plains and deep blue skies. The historic (circa 1850) property was chosen by researchers to build two “pathfinder” radio telescope arrays with a size of about 1% of the final SKA. The Australian SKA Pathfinder (ASKAP) and the Murchison Widefield Array (MWA) have been testing out the new technologies needed to build the SKA, establish the quality of the site for astronomy and making their own contributions to radio astronomy as new unique instruments. By 2019, construction of Phase 1 of the SKA is expected to start in the MRO, as well as at a second site in the Karoo region of South Africa.

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