Sunset in the outback: SkyMapper enclosure on the peak of Siding Spring Mountain, NSW. ANU's 2.3 m telescope can be seen in the background.

Credit: P.Tisserand, RSAA.

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NASA satellites detect a burst of gamma ray energy from a supernova. They relay the exploding star's coordinates to the new facility, called SkyMapper. The unmanned optical telescope rotates to focus on the supernova, one of the most violent objects in the universe. It will take pictures of the blast to add to a collection recording the history and evolution of the cosmos.

Some of SkyMapper's biggest insights, however, are expected to come from more recent events and objects closer to home.

The Australian National University in Canberra is constructing the A$12.5 million telescope – which will start work in September – at Siding Spring, near Coonabarabran in northern New South Wales.

SkyMapper will replace the historic Great Melbourne Telescope, destroyed when the 2003 Canberra bushfires swept through the Mount Stromlo Observatory (see, Storms of fire, Cosmos Online).

With light pollution increasing in Canberra, the university decided to build the telescope at Siding Spring – considered the best dark sky location in the country because of the low level of atmospheric 'shimmer' and its remoteness to coastal clouds.

Near the Warrumbungle Ranges, Siding Spring is the site of the Anglo-Australian Observatory and other major telescopes.

Southern Sky Survey

The telescope's main task will be to conduct the first systematic survey of the entire southern sky to produce a detailed digital map.

Since SkyMapper will be sensitive enough to pick up some of the most distant, faintest objects, the chart will have a deep time dimension.

Because of the time it takes light waves to reach Earth, the Southern Sky Survey will enable astronomers to look back to the time soon after the Big Bang when the first stars' nuclear fusion reactions set the primeval universe ablaze. This was the time when stars were beginning to manufacture the heavy elements from hydrogen, including iron and the element that billions of years later would form the basis of life on Earth.

Another strength of the telescope is a set of coloured glass filters, designed by ANU astronomers and engineers, to analyse the starlight to determine the star's chemical composition, temperature and density. The filters will enable scientists to pinpoint stars with low concentrations of heavy elements, says ANU astronomer Stefan Keller.

"Successive generations of stars return heavy elements to the interstellar gas and this is incorporated in future stars," he says. "SkyMapper will search for stars with the lowest proportion of heavy elements to find the oldest stars. These will give us insight into the way the universe was first lit up by stars and how galaxies form."

These stars are very rare – about 100 in a billion, says Keller.