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NC telescope to be ‘major actor’ in field of cosmology

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“The SKA will be the first radio telescope to be a major actor in the field of cosmology”

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THE SQUARE Kilometre Array (SKA) radio telescope, being constructed in the heart of the Northern Cape, will be “a major actor in the field of cosmology” and could produce the first ever map of the large-scale structure of the universe back to a time when it was 2.2 billion years old.

This is according to a new paper published that highlights the potential of the SKA to tackle key questions of cosmology, by presenting a detailed overview of the various observation campaigns that can be conducted with the telescope once built.

Cosmology is the study of the origin and fate of the universe. Cosmologists believe that ordinary matter – the matter that forms everything we see including planets and galaxies – only accounts for around 5% of the total mass and energy content of the universe. 

Two mysterious components seem to constitute the rest with dark matter – matter we can’t see directly but whose gravitational effects on normal matter we can observe – constituting around 27% of the remaining content and dark energy – the force causing the universe to expand at an accelerated rate – accounting for the remaining 68%.

The Red Book, as it is called, is the product of the SKA’s Cosmology Science Working Group, a group of around 130 scientists from 70 different institutes in 19 countries interested in using the SKA that represents the wider cosmology community. It builds on the work of the 2015 SKA Science Book, taking into account the major developments in the field since then. 

With 46 authors from 36 institutes contributing directly to the writing of the paper, it represents a significant piece of work on the science potential of the SKA to address key issues in cosmology such as dark matter and dark energy.

“We know the universe is expanding at an accelerating rate, but we don’t yet understand why,” Professor Richard Battye, co-chair of the working group from the University of Manchester, explained.

“One of SKA’s main science goals is to investigate this, by looking at the distribution of the most basic element, hydrogen, throughout the cosmos. We hope to go beyond what is now considered the ‘standard’ cosmological model and further refine our estimates of the amounts of dark matter and dark energy at any given time in the universe,” Battye stated.

The Red Book details the cosmological surveys that the SKA will carry out, and the science they will enable, including establishing the proportion of dark energy in the universe thanks to percent-level precision measurements of its expansion rate over the last 12 billion years.

“Science is a constantly evolving field, so we have to update our research to reflect new discoveries and the advance of techniques,” SKA project scientist Dr Anna Bonaldi, a co-author of the paper, added.

“As we near the start of construction, the design of the SKA has also matured, so this needs to be reflected in our predictions.”

There have been major discoveries in the past few years which have implications for the field of cosmology, including the detection of gravitational waves predicted by Einstein, by the Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO) in the United States, and the detection by the EDGES experiment located on the site of the future SKA-low telescope, in Western Australia, of what could be the signal from some of the first stars to form in the universe, one of the key science goals of the SKA.

These discoveries bring new questions within cosmology, especially on the nature of dark matter. Astronomers are now working on their observational implications and how the SKA could help to confirm the results, in particular through synergies with other upcoming groundbreaking telescopes which observe the universe at different wavelengths.

“The SKA will be the first radio telescope to be a major actor in the field of cosmology,” Dr Laura Wolz, co-chair of the working group and a Research Fellow at the University of Melbourne, said.

“With it we’ll be able to produce the first ever map of the large-scale structure of the universe back to a time when it was 2.2 billion years old – this is incredibly exciting for cosmologists, as it will enable new science and unpredicted discoveries,” she concluded.

The SKA project is an international effort to build the world’s largest radio telescope, with eventually over a square kilometre (one million square metres) of collecting area. The Northern Cape’s Karro area, close to Carnarvon, was chosen as one of the co-hosting locations, for many scientific and technical reasons, from the atmospherics above the site through to the radio quietness which comes from being one of the most remote locations on Earth.