alive and well - Geological Society of Australia

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Radio waves are suited to the study of the cosmos fora number of reasons. Radio waves, as for visible light, penetratethe Earth’s atmosphere whereas radiation at most other wavelengthsis absorbed. The long wavelengths of radio waves can alsopenetrate cosmic dust, allowing astronomers to look into regionssuch as the centre of our own galaxy, the Milky Way, or the heartof a distant nebula where stars are being born. Therefore radioastronomy affords a more comprehensive view of the cosmos.Bigger really is betterThe snag of course is that the further objects are away, the harderthey are for us to detect and for their structures to be resolved.The bigger the telescope, the better our view of the cosmos andthe further back in time our scientists can peer. In the early1990s, astronomers pondering the next big thing calculated thata radio telescope with a collecting area of one square kilometrewould allow observations of the infant Universe. Clearly animpossibly cumbersome structure to build and manipulate as asingle radio dish to scan the sky, but luckily there is a way toachieve this collecting area through a technique known as‘interferometry’.The premise behind this technique is to build a series of moremodestly sized radio telescopes and join them by fibre optics towork together as one giant telescope. The concept is similar toinsect eyes, where the separate components are wired up to givea continuous image. Hence the concept of a Square KilometreArray (SKA) was born over 20 years ago.The biggest of the lotThe SKA will be made up of about 3 000 dish-shaped antennas(similar to Parkes, except these are 15 m wide), which are goodat detailed study of smaller regions of space. It will also have twoother novel radio telescope designs called Aperture Arrays, whichhave very good views of large sections of the sky at once. Whenfinished, the SKA will have more than 2.5 million Aperture Arrayantennas.Earlier this year, a decision on the SKA’s location wasannounced, ending a many-year process to choose betweenprospective sites in Southern Africa and Australia–NZ. The finaldecision was a win–win, with the dish-shaped antennas of theSKA to be built in Africa and the lower frequency collectingAperture Arrays to be built in Australia and New Zealand.This decision plays to the strengths of both locations, andrecognises the large amount of work happening in Australia andNew Zealand to develop the technology that will be needed forthe low-frequency portions of the SKA. Aperture-Array-styletelescopes are a new type of radio telescope that is onlyjust beginning to be possible on a large scale, whereas dishtechnology has been around for a very long time (which the51-year-old Parkes Observatory can attest to!)Window to the UniverseWhen complete in 2024, and in fact along the way as well, theSKA will be capable of some incredible science. It will revealsecrets about ‘big issues’ such as the evolution of the Universe;The Parkes radio telescope viewed from the visitors’ area. Image publicdomain via Wikimedia Commons.how galaxies form, evolve and die; and the nature of the earlyUniverse. It is a time that astronomers refer to as the Dark Ages.Not the pre-Medieval times in our history books but a Universeyet to form stars and which is therefore invisible to our opticaltelescopes. The SKA will literally detect the first light from thefirst stars to ‘switch on’ in the Universe. Other insights includeprobing the fundamental laws of physics, beyond the laws ofNewton, Einstein or quantum physics and the search for‘signatures’ of life through the detection of molecules such asmethane. Then of course comes the discovery of the unknownand the unexpected, equivalent to the discoveries about livingthings seen through the first microscopes.As fascinating as such observations are, the SKA is also likelyto have more direct benefits for us Earth-bound beings. Of coursewe cannot predict what these might be, although judging by therecent record of radio astronomy, it is likely to pack quite a punch.Thanks to the brilliance of Australian CSIRO radio astronomerDr John O’Sullivan, radio astronomy has already brought theworld WiFi. Other discoveries stemming from radio astronomyinclude sophisticated medical imaging techniques and satellitenavigation to guide our car journeys.TAG September 2012| 29
Three dishes of ASKAP at the Murchison Radioastronomy Observatory, WA.Image courtesy of the Department of Commerce, Western Australia.A tile of the Murchison Widefield Array (MWA). Each antenna is about 50 cmhigh. Image courtesy Dr Natasha Hurley-Walker, International Centre for RadioAstronomy Research (ICRAR).Finding the pathUntil SKA construction begins in 2016, astronomers andengineers will continue to concentrate on the two precursortelescopes under construction at the Australian SKA core site,the Murchison Radioastronomy Observatory in WA. One is theCSIRO’s Australian SKA Pathfinder (ASKAP). Consisting of36 dish antennas 12-m-wide ASKAP is a proving ground forSKA technology with its novel ‘radio cameras’ as well as beingone of the fastest telescopes to survey the sky. It will becompletely operational in 2013.The other precursor is the Murchison Widefield Array(MWA), a pathfinder to the low-frequency Aperture Arrays ofthe SKA that will be dotted from the SKA’s Australian core inthe Murchison all the way over to New Zealand. The MWA’sunique design has no moving parts and relies on computingpower to point the telescope to different sections of sky. Lookinglike metal spiders about 50 cm high, the MWA’s 4096antennas are spread over a region about 3 km wide. It will lookfor changing ‘blips’ called transient sources, observe Solarweather in space and look for some of the earliest signalsproduced in the Universe. The MWA will start full scienceoperations sometime in the next six months.It’s often said within science that ‘we’re at the dawn of newdiscoveries’, although this time it couldn’t be truer. The SKA andits precursors will increase our capacity to observe the Universeby an unheard-of amount in the history of astronomy, and themost exciting things it will discover are probably things wecan’t even imagine today. It’s an exciting time to be around!KIRSTEN GOTTSCHALK30 |TAG September 2012
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