Astronomical events

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Astronomical events

Posted 4/06/2012 by Matthew James

Some 242 years ago, Captain James Cook explored the eastern coast of Australia, after having been sent to the South Pacific Island of Tahiti to observe the transit of the planet Venus in 1769. He was sent there partly in order to help astronomers of the day estimate the size of the solar system. Australia’s long and distinguished association with astronomy had begun.

On 6th June 2012, just before 8:30 am along the east coast of Australia, the tiny dot of the planet Venus will again pass slowly across the face of the Sun, as seen from Earth. Such ‘Transits of Venus’ are infrequent events; the next transit does not occur until 2117 so this is one for us to savour. Many smaller observatories here will be trained on this solar event.

While some of us will look carefully and indirectly at the Sun’s reflections using our appropriately shielded eyes and telescopes, (so as to avoid blindness - do not use sunglasses, smoked glass, exposed film or CD/DVDs as filters; and never look at the Sun through normal telescopes, eyepieces or binoculars) much of modern astronomy relies on radio frequency observation. This is achieved through radio telescopes in which Australia has played a large part in astronomical developments, such as the Australia Telescope which is trained on galactic events occurring in the deepest recesses of the Universe.

Square Kilometre Array
Now Australia has been selected, with South Africa and other participating nations, to help develop the next generation of radio telescopes – the Square Kilometre Array (SKA). This is not just a single telescope but an enormous system of interlinked separate receivers. It will be up to 50 times more sensitive than the best present-day instruments. It will comprise a vast array of antennas, arranged in clusters to be spread over thousands of kilometres. The antennas will be linked electronically to form one enormous telescope.

The SKA is a collaboration between institutions in 20 countries (including Australia, New Zealand and countries in Europe, Asia, Africa, and North and South America), led by an international science and engineering committee and a jointly-funded SKA Project Office. A formal Australian SKA Consortium was established in 2001. Australian research institutions currently involved with the SKA project include CSIRO, the University of Sydney, the Australian National University and Swinburne University of Technology.

In December 2005, four countries (Australia, Argentina, China and South Africa) submitted proposals to the International SKA Steering Committee (ISSC) to host the SKA. On September 28, 2006, it was announced that Australia and Southern Africa had been short-listed as acceptable sites to host the SKA – the final decision was left to be made in 2012.

On 25 May 2012, in the Netherlands, the decision was announced that South Africa would share the SKA with Australia and New Zealand. The South African team had highlighted how locating the facility in Africa would act as beacon for science in the continent. It appears that the bulk of the initial phase of construction from 2016 to 2020 will be in Africa, with Australia to consolidate its initial demonstrator facility and provide antenna technologies.

However, the cost and complexity of the second phase may prove more difficult to overcome. It will cost some $2 billion to build and perhaps $25 billion to maintain aver the next 50 years, paid for by the consortium. Given global economic conditions, a question has already been raised about the future funding of the larger project. The Australian Government in the 2011 Federal Budget committed $40.2 million over four years, to support the Joint Australia-New Zealand bid. According to Senate Estimates of 26 May 2012 (pp. 96–97), overall Australia has already spent some $150 million on the project (earlier stated as $130 million in the ASA Briefing for Science Meets Parliament 2011: Australian Astronomy Statistics).

Astronomical technology
Few astronomers peer through a telescope these days as most observing is computerised and often remotely based. Much observing activity in Australian optical astronomy occurs at Siding Spring Observatory and the Australian Astronomical Observatory located near Coonabarabran NSW, where a large number of significant telescopes and facilities coexist. Our principal radio astronomy facilities are also in NSW at Parkes and Narrabri. Australia has a gravitational wave observatory north of Perth. Astronomy also involves theoretical study, instrumentation development and teaching at many local tertiary institutions.

The Australian Astronomy Decadal Plan 2006-15 adopted a strategic vision for national benefit through research and expertise in optical and radio facilities, with a focus on international collaborations and global projects located here and elsewhere. The major two future projects are the Square Kilometre Array (SKA) radio telescope program and the development of Extremely Large Telescope (ELT) optical facilities at overseas locations.

Radio telescopes are very sensitive devices that measure the intensity of radio waves over a band of frequencies. Their antennas are often in the shape of a ‘dish’ or cylindrical reflector to provide a large collecting area. The radio waves are reflected off the collector surface and are focused onto a receiver.
When two (or more) signals are combined from separate antennas the telescope is known as an interferometer. Signals from an interferometer can be electronically combined to simulate a single dish of a size equal to the largest antenna separation – the bigger the separation, the better the resolution of the image that can be produced. The sensitivity of an interferometer increases as the total amount of collecting area increases. This is one reason why the SKA will be a powerful radio telescope as it will have the collective power of many ground units. (ANZSKA factsheet)
The Australian site for the main focus is in the mid west of Western Australia, within the Shire of Murchison, some 300km north of Geraldton. This region is said to be one of the few places in the world today that is suitable in terms of its radio-quietness and its radio-astronomy observational qualities. The CSIRO SKA demonstrator project located there is now named ‘ASKAP’ – the Australian SKA Pathfinder telescope. Astronomers from around world are already lining up to use the ASKAP’s 36 antennae and the first five years of its operation are, apparently, already booked out!


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