alive and well - Geological Society of Australia
alive and well - Geological Society of Australia
alive and well - Geological Society of Australia
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Radio waves are suited to the study <strong>of</strong> the cosmos fora number <strong>of</strong> reasons. Radio waves, as for visible light, penetratethe Earth’s atmosphere whereas radiation at most other wavelengthsis absorbed. The long wavelengths <strong>of</strong> radio waves can alsopenetrate cosmic dust, allowing astronomers to look into regionssuch as the centre <strong>of</strong> our own galaxy, the Milky Way, or the heart<strong>of</strong> a distant nebula where stars are being born. Therefore radioastronomy affords a more comprehensive view <strong>of</strong> the cosmos.Bigger really is betterThe snag <strong>of</strong> course is that the further objects are away, the harderthey are for us to detect <strong>and</strong> for their structures to be resolved.The bigger the telescope, the better our view <strong>of</strong> the cosmos <strong>and</strong>the 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 <strong>of</strong> one square kilometrewould allow observations <strong>of</strong> the infant Universe. Clearly animpossibly cumbersome structure to build <strong>and</strong> 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 <strong>of</strong> moremodestly sized radio telescopes <strong>and</strong> 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 <strong>of</strong> a Square KilometreArray (SKA) was born over 20 years ago.The biggest <strong>of</strong> the lotThe SKA will be made up <strong>of</strong> about 3 000 dish-shaped antennas(similar to Parkes, except these are 15 m wide), which are goodat detailed study <strong>of</strong> smaller regions <strong>of</strong> space. It will also have twoother novel radio telescope designs called Aperture Arrays, whichhave very good views <strong>of</strong> large sections <strong>of</strong> 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 <strong>and</strong> <strong>Australia</strong>–NZ. The finaldecision was a win–win, with the dish-shaped antennas <strong>of</strong> theSKA to be built in Africa <strong>and</strong> the lower frequency collectingAperture Arrays to be built in <strong>Australia</strong> <strong>and</strong> New Zeal<strong>and</strong>.This decision plays to the strengths <strong>of</strong> both locations, <strong>and</strong>recognises the large amount <strong>of</strong> work happening in <strong>Australia</strong> <strong>and</strong>New Zeal<strong>and</strong> to develop the technology that will be needed forthe low-frequency portions <strong>of</strong> the SKA. Aperture-Array-styletelescopes are a new type <strong>of</strong> 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, <strong>and</strong> in fact along the way as <strong>well</strong>, theSKA will be capable <strong>of</strong> some incredible science. It will revealsecrets about ‘big issues’ such as the evolution <strong>of</strong> the Universe;The Parkes radio telescope viewed from the visitors’ area. Image publicdomain via Wikimedia Commons.how galaxies form, evolve <strong>and</strong> die; <strong>and</strong> the nature <strong>of</strong> 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 <strong>and</strong> 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 <strong>of</strong> physics, beyond the laws <strong>of</strong>Newton, Einstein or quantum physics <strong>and</strong> the search for‘signatures’ <strong>of</strong> life through the detection <strong>of</strong> molecules such asmethane. Then <strong>of</strong> course comes the discovery <strong>of</strong> the unknown<strong>and</strong> 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 <strong>of</strong> radio astronomy, it is likely to pack quite a punch.Thanks to the brilliance <strong>of</strong> <strong>Australia</strong>n CSIRO radio astronomerDr John O’Sullivan, radio astronomy has already brought theworld WiFi. Other discoveries stemming from radio astronomyinclude sophisticated medical imaging techniques <strong>and</strong> satellitenavigation to guide our car journeys.TAG September 2012| 29