Astronomers will soon be able to listen in on the universe with the most powerful radio telescope ever built: the Square Kilometre Array (SKA), which is nearing completion.
With a large number of antenna dishes spread across the world, the SKA’s baseline extends over a million square metres, with its central control units located in the flat plains of Western Australia and the Karoo region of South Africa. This makes it a virtual parabolic dish antenna with a diameter as wide as Earth.
When this gigantic ‘dish’ becomes operational in 2024, it will be able to detect radio signals emitted by sources billions of lightyears away. This will push the boundaries of radio astronomy and bring the universe into a much sharper focus which is just a dream for astronomers now.
Several countries are members of the SKA organisation, including Australia, Canada, China, India, Italy, New Zealand, South Africa, Sweden, the Netherlands and the UK. India, incidentally, has played a key role in setting up the SKA. The National Centre for Radio Astrophysics of the Tata Institute of Fundamental Research led the international team which designed the all-important Telescope Manager: the master control that runs the SKA’s operations.
Although radio waves are ‘invisible’ to the eye, radio telescopes can pick them up even from billions of light years away and change them into images. Connected by fibre optic cables, the combined data from the arrayed dishes of the SKA peppered across several landscapes are crunched by supercomputers to locate and image sources in the sky accurately. Ever since the American astronomer Karl Jansky first detected radio signals from space in the 1930s, astronomers have used radio telescopes to study radio waves emanating from various objects in space and unravel the secrets of the universe. It is thanks to radio astronomy that we know more about the structure and nature of pulsars (fast spinning neutron stars), the cosmic microwave background (signals left over from the time of the universe’s birth) etc. Using the SKA, scientists will be able to study these in detail, besides continuing the search for extra-terrestrial life by observing the heat emissions from planets orbiting young stars. They will also have an excellent opportunity to resolve one of the greatest cosmic puzzles: the mystery of the missing mass.
Once upon a time, astronomers believe, everything in the cosmos must have been condensed into an infinitesimally small blob in the void. Accepted theory has it that this incredibly dense speck exploded with a “Big Bang” to engender the universe as we know it. The resulting fireball cooled as it spread and its blinding light faded into a gathering darkness so that, at some point, the young universe resembled a formless sea of murky matter, highlighted only by traces of primordial hydrogen and helium. This darkness persisted from some 300,000 to half a billion years after the Big Bang, which is why there’s so little direct evidence today of this important period in the cosmic story.
Light probably returned to the heavens when the first stars lit their nuclear fires and the universe continued to expand. This expansion is now discernible in a faint glow of microwave radiation – the oldest light in the universe – which astronomers have captured using terrestrial radio telescopes and satellites. But scientists studying this ancient light are mystified by calculations that show that everything we see accounts for a mere 5% of the total matter-energy content of the universe. Of the rest, 30% is believed to comprise “dark matter” (which doesn’t quite radiate, but holds together the galaxies and clusters of galaxies like some kind of cosmic glue). And the remaining 65%? This is thought to be “dark energy” – a mysterious repulsive ‘force’ that pushes galaxies away from each other at an ever-increasing speed. It is through this celestial mist that the SKA will peer to investigate the mysteries of dark matter and dark energy and provide scientists with the most detailed images yet of the early days of the universe.
But before the SKA’s antennas flicker to life and begin gathering the first bits of data, scientists have to overcome several technical challenges that stand in their way. Collecting, linking and analysing the data, for instance, is a mammoth task as the SKA will eventually generate more data flow than the entire World Wide Web. Another huge challenge is to resolve the problem of radio noise in the SKA’s operations. Terrestrial radio disturbance from sources like cell phones, television and airport radars all create a noisy radio environment, making it very difficult for radio telescopes to record sensitive astronomical measurements. The 250-foot radio telescope at Jodrell Bank, for example, could easily pick up the tiny bit of energy from a cell phone placed on Mars! The SKA’s mind-boggling sensitivity compounds the problem manifold. In fact, it is to minimise terrestrial radio interference that the control elements of the SKA have been split across two remote sites.
A possible solution is to set up more ‘international radio quiet zones’ where slices of the radio spectrum are reserved exclusively for receiving natural signals from space. The National Radio Astronomy Observatory in West Virginia, US, is located in a National Radio Quiet Zone, where cell phone service doesn’t exist and broadcast radio transmitters point their antennas away from the observatory. Similar radio quiet zones have also been demarcated in countries like Australia and Brazil. Such efforts would be crucial for the SKA as it extracts from a hiss of static the elusive electromagnetic whispers that tell us of the early universe.
Prakash Chandra is a science writer.