Astronomy has big ambitions. Soon its new telescopes will stretch across continentsby Pedro Ferreira / May 4, 2009 / Leave a comment
A computer simulation of SKA focal plane arrays and small dishes, 2008
It’s like a page torn from a Dan Dare comic strip, where the undeveloped world meets the ultra future: a barren landscape of rock and bush, peppered with radio antennae so sophisticated they have yet to be invented. But it won’t be on another planet, or involve space travel. Rather, it will be the world’s most sophisticated telescope—a series of hundreds of antennae stretching across thousands of kilometres of Australian or southern African desert.
The planned square kilometre array, or SKA, is a giant camcorder scanning the sky in all directions to pick out every galaxy visible on the earth’s cosmic horizon. Its many separate dishes will simulate a single giant telescope, with a central “collecting area” of one square kilometre capable of capturing electromagnetic waves from the outer reaches of space.
The current generation of telescopes pick up only about 5 per cent of the universe’s energy and matter; the vast majority remains invisible or dark. Cosmologists think that unravelling this dark world will allow us to understand both the history of the universe and the formation of galaxies such our own. A range of new projects aim to help to solve this central problem of modern cosmology, namely establishing what, and where, dark matter and energy is. The SKA, originally conceived in the 1990s by a group of scientists from 19 countries, has become the poster child for such “big astronomy.” Today’s telescopes can provide different windows on the universe, but not a single picture. The SKA, if built, could turn this incomplete vision into a new map of the universe.
Similar projects include optical telescopes with collecting areas around a hundred times larger than today’s; and (under discussion at the European Space Agency and Nasa) a new wave of scientific satellites armed with new instruments capable of looking more accurately and more deeply into space. The hope is that this image of the entire universe will allow scientists to reconstruct how its different building blocks—from individual planets to whole galaxies—assembled into one coherent whole. This in turn, should help to tease out the nature of dark matter and energy itself.
At present the SKA remains a theoretical venture; getting it up and running means solving a series of daunting technical problems. Its planned design would see the majority of its radio antennae clustered in one central site, comprising a few hundred stations. The daily flow of data to each station would match the data passing through the entire internet today. Each station will need a supercomputer capable of performing more than a quadrillion—or one thousand million million—mathematical calculations per second, well beyond the capacity of contemporary machines.
But the challenges will be geopolitical too. Smaller substations would radiate outwards from the SKA’s central cluster, in spiral arms many thousand of miles long. If built in South Africa, these arms would penetrate far into neighbouring Namibia, Botswana and Mozambique (the plans bypass Zimbabwe) ending up as far away as Ghana, Kenya and the island of Mauritius. To succeed the SKA needs stable politics and stable funding: any country pulling out would damage the whole project.
But big astronomy is equally challenging to astronomers themselves, many of who feel a wistful nostalgia as their field moves away from individual observers, collecting data on mountain tops with simple homemade telescopes on clear nights.
American radio engineer, Grote Reber, built one of the first radio telescopes in his backyard during the 1930s. After the second world war, British scientists applied the expertise gained studying radar to astronomy instead. Such astronomers at Cambridge university would spend staff away days at an observation station near Lord’s Bridge in the Cambridgeshire countryside, hammering wooden stakes into the ground, connecting them with lengths of wire to create one of the first large “radio arrays,” a precursor to the SKA. It was here that astronomers Anthony Hewish and Jocelyn Bell Burnell found the first pulsars, the densest known objects, made entirely of neutrons. Their discovery opened up a new window on the laws of physics that may have been at play in the very first moments of the universe.
Yet it is these same astronomers who now join complex international consortiums, pushing ahead with projects like the SKA. Ditching their heritage of tinkering in small teams also means acquiring a new taste for big spending, at a time when governments are strapped for cash. The site for the SKA isn’t decided yet; the choice between Australia and South Africa will be made around 2012. The cost, however, is clear. With a planned budget exceeding £1bn, it’s not just the telescopes that are growing in size and ambition.