SKA and UWC scientists probe the universe with SKA
When the Square Kilometre Array (SKA) comes online, it will be a telescope unlike any other – 50 times more sensitive than any other radio instrument, able to survey the sky thousands of times faster and more accurately than ever before, and very, very big (the SKA name comes from the fact that it will be composed of a variety of smaller instruments that collectively form a telescope with a combined collecting area of about one square kilometre).
Powerful enough to sense radio waves from objects millions or even billions of light years away from Earth, the SKA telescope will allow scientists to look further back into the history of the universe than ever before, and will give much more detail on how the universe has evolved over the last 14 billion years, and how stars, galaxies and galaxy clusters have formed and changed since the Universe was young.
The international SKA organisation includes 11 countries – and South African scientists are playing a leading role in many SKA projects together with astronomers from the other SKA member countries. Roy Maartens, SKA Research Professor at the University of the Western Cape (UWC) and also chair of the SKA Cosmology Working Group, and Mario Santos, a Research Professor from UWC, have played a leading role in setting out the cosmological science that can be done with the SKA.
“Researchers here have devised a means of using the world’s largest telescope in new ways that will help shape the future of cosmology,” says Prof Maartens.
“Usually a map of the Universe is made using galaxies as tiny beacons of the large scale of the Universe,” explains Santos. “This is quite demanding as it requires the mapping of large numbers of galaxies across the sky. But the survey we are proposing will measure the emitted radiation from all the hydrogen atoms spread across the Universe without actually detecting galaxies. This will make it easier to survey all of the sky across cosmic time, allowing phase 1 of the SKA to become an extremely competitive cosmology machine.”
By making these huge 3D maps of the Universe, the researchers will be able to test the limits of General Relativity and maybe find some signature of the new physics on these large scales which can shed light on the true nature of dark energy. Moreover, they can also look for imprints of what happened at the very beginning of the Universe.
“It will be like making a movie of the Universe from a young age, when it was only about 2 billion years old, until today, when it is about 14 billion years old,” Maartens adds. “The movie will be low resolution, but good enough to test the fundamentals of cosmology.”
An experiment like this, using intensity mapping, has never been done before. The largest 3D maps of the large scale structure of the Universe have been created using optical telescopes. The current project will be about 50 times larger – and while other future experiments will also be able to probe a large fraction of the Universe, but none will match the SKA in terms of size and depth.
Once phase 1 of the SKA is built, around 2022, it will take about two years to complete the survey, and a large team will be required to deal with it. SKA SA has been crucial in promoting the build-up of the researchers required to lead such an effort. But they don’t have to wait for the SKA to start before doing observations. Tests are already being conducted using the KAT7 system with the full support of the KAT7 staff and Santos and fellows plan to start tests with MeerKAT in just a year, during the early science phase.
And as Santos notes, the SKA telescope is “like a physics lab”, allowing many different experiments to be pursued that, in combination with this one, will allow scientists to push the limits of our current knowledge of the Universe.
“The scientific knowledge that will come from the SKA – knowledge about our Universe and our place in the Universe – will be shared amongst all scientists and taken to the public in all countries,” says Maartens.
“It will be available to everyone, without charge, and it will enrich humanity, in a similar way that music, literature, art and all other forms of knowledge enrich us. The SKA is an investment in the knowledge and culture of all humanity.”