Construction begins on world’s largest radio telescope, the Square Kilometre Array

After 30 years of planning and negotiations, the foundations of the SKA are now being laid across sprawling sites in Australia and Africa, with its headquarters to be established in the UK.

The gigantic observatory is set to be completed in 2028, when it will begin collecting the radio signals emitted by celestial objects to shed light on some of the most enigmatic problems in astronomy, such as the nature of dark matter and how galaxies form.

Astronomers and local communities have travelled to the remote sites in South Africa’s Northern Cape and Western Australia to celebrate the milestone with officials from the SKA Observatory (SKAO), the intergovernmental organisation in charge of the telescopes.

“We’re basically setting the foundation of this instrument for the next 50 years,” said Lindsay Magnus, the director of the telescope being built in South Africa. “That’s the exciting part: this is a long-term legacy.”

The SKA telescopes will initially comprise 131,072 antennas in Australia (known as SKA-Low), which will be built at Inyarrimanha Ilgari Bundara, on Wajarri Country in Western Australia, and 197 dishes to be built in the Karoo in South Africa (known as the SKA-Mid).

When finished, the observatory will consist of thousands of dishes and up to a million low-frequency antennas that will enable astronomers to monitor the sky in unprecedented detail and explore the first billion years after the so-called ‘dark ages’ of the Universe.

“The concept for the SKA dates back to the early 1990s and although the original name remains, the science goals, concept and engineering behind the project have evolved over the years, resulting in the science requirements of today that call for 130,000 antennas and 200 dishes,” the SKA Organisation said.

Although the project has been in the planning stages for three decades, it was only in November 2022 that the traditional custodians of the Murchison region in Western Australia gave their consent to the radio telescope being built on their ancestral lands. 

“We are truly grateful to the Wajarri Yamaji for agreeing to host the telescope on their land,” said Philip Diamond, SKAO’s director-general professor. 

“We honour their willingness to share their skies and stars with us as we seek to find answers to some of the most fundamental science questions we face. We commit to respecting their connection to the land and preserving and protecting their cultural heritage.”

The placement of the radio telescope was selected in 2012, when the SKAO settled on two sites in South Africa and Australia to co-host the facility, taking advantage of the lack of human-generated radio waves in remote regions for clear observations of the cosmos.

The large distances between antennas, and their sheer number, mean that the telescopes will pick up radio signals with unprecedented sensitivity.

While SKA-Low will detect frequencies between 50 megahertz and 350 megahertz,  SKA-Mid is set to pick up frequencies between 350 megahertz and 15.4 gigahertz. Both are interferometers, in which many dish-shaped antennas together act as a single telescope.

“To put the sensitivity of the SKA into perspective, the SKA could detect a mobile phone in the pocket of an astronaut on Mars, 225 million kilometres away,” said Dr Danny Price, senior postdoctoral fellow at Australia’s Curtin Institute of Radio Astronomy.

“More excitingly, if there are intelligent societies on nearby stars with technology similar to ours, the SKA could detect the aggregate ‘leakage’ radiation from their radio and telecommunication networks – the first telescope sensitive enough to achieve this feat.”

The SKA will be built in stages. The €1.3bn (US$1.4bn) first phase is expected to be completed in 2028, when four dishes in Australia and six antenna stations in South Africa are made to work seamlessly together as a basic telescope, covering an area of just under 500,000 square metres.

As one of the largest scientific endeavours in history, the SKAO brings together more than 500 engineers and 1,000 scientists in more than 20 countries. Over £15m has been awarded to UK institutions, including the University of Manchester, to deliver the software ‘brain’ of the world’s largest radio telescope as it moves into the construction phase.

When completed, each of the two SKA telescopes is expected to produce enough data to fill a typical laptop hard drive every second, which will be processed by China’s Tianhe-2 supercomputer. 

The total collecting area of the telescope will be approximately one square kilometre, giving 50 times the sensitivity and 10,000 times the survey speed of the best current-day telescopes.