A ‘major scientific step forward’: Work has finally begun on building the world’s largest radio observatory

Artists’ impression of the SKA-Low antenna arrays.Credit: DISR

After 30 years of planning and negotiations, construction begins this week on the Square Kilometer Array (SKA), the world’s largest radio astronomy observatory. The giant instrument — which will be built across sprawling sites in Australia and Africa — will collect radio signals emitted by celestial bodies and hopefully shed light on some of astronomy’s most enigmatic problems, such as the nature of dark matter and how galaxies form.

On Monday, astronomers and local communities will travel to remote sites in South Africa’s North Cape and Western Australia to celebrate the milestone with officials from the SKA Observatory (SKAO), the intergovernmental organization responsible for the telescopes.

“We’re laying the foundation for this instrument for the next 50 years,” says Lindsay Magnus, director of the telescope being built in South Africa, based in Cape Town, South Africa. “That’s the exciting part — this is a long-standing legacy.”

years in the making

In 2012 it was decided that what was initially envisioned as a single giant telescope would consist of two instruments, one in South Africa and one in Australia. The great distances between the antennas, and their sheer number, mean that the telescopes — called SKA-Mid and SKA-Low, respectively — will pick up radio signals with unprecedented sensitivity. SKA-Low will detect frequencies between 50MHz and 350MHz and SKA-Mid will pick up frequencies between 350MHz and 15.4GHz. Both are interferometers, in which several dish-shaped antennas work together as a single telescope.

SKA will be built in phases, with the €1.3 billion (US$1.4 billion) first phase expected to be completed in 2028. Another €700 million has been earmarked for operating costs of the telescopes over the next decade. The ultimate goal is to have thousands of dishes in South Africa and African partner countries, and one million antennas in Australia, with a total collection area of ​​one square kilometre. The first phase is about a tenth of the total planned project.

SKA- Low

The SKA-Low telescope, in Australia, will consist of about 131,000 antennas, each resembling Christmas trees with two-meter wires. More than 500 arrays of 256 antennas will dot the red sands of the site, which has been renamed Inyarrimanha Ilgari Bundara, CSIRO Murchison Radio Astronomy Observatory. “Inyarrimanha Ilgari Bundara”, the name chosen by the traditional owners of the land, Wajarri Yamaji, means “sharing the sky and the stars”.

Earlier this month, Wajarri Yamaji and the Australian government registered a land use agreement allowing the telescope to be built on Wajarri Yamaji’s land. Local residents will act as heritage monitors and escort SKAO officials before any ground disturbance during construction, says de Mongo, a member of the Wajarri Yamatji community looking to get the work started. “Once they start building, there are opportunities for Wajarri people to get involved in business and business opportunities.”

Scientists are also eager for the antennas to start collecting data. “[SKA-Low’s] The sensitivity will allow us to observe the distant universe in much more detail than anything we’ve done so far,” says Douglas Bok, director of space and astronomy at the Commonwealth Scientific and Industrial Research Organization (CSIRO) in Sydney, Australia. “This is particularly exciting because we know so little. about the first billion years of the universe.

But the most exciting science will be phenomena we “didn’t know existed” when the telescopes were designed, predicts Sarah Pearce, director of the Perth-based SKA-Low Telescopes. The first four arrays will collect data by 2024, and all arrays will be completed by 2028.

South African dishes

On Monday, preparations for the construction of the first giant SKA-Mid dishes will also begin. These will form an array of 197 antennas, spanning more than 150 kilometers in the dry Karoo region of South Africa. Four will be completed in 2024, and more will be added by 2028.

There is already a 64-dish MeerKAT telescope in South Africa on site, and it will be integrated into SKA-Mid. In early 2022, using MeerKAT data, an international team published the most detailed image yet of the center of our galaxy.1, and the Milky Way, as well as images of mysterious radio filaments emanating from the galaxy’s black hole. The South African government and the German Max Planck Society are adding 20 more dishes to the telescope, as part of an expansion project. MeerKAT will be integrated into SKA-Mid only at the end of its construction in 2027.

“SKA would be a great scientific step forward,” says Erwin de Block, an astronomer at the Netherlands Institute for Radio Astronomy in Duingelo and principal investigator of MeetKAT’s MHONGOOSE Large Survey program looking at galaxy formation. SKA-Mid will help us study nearby galaxies in great detail and directly reveal the flow of gas into galaxies and the processes that lead to star formation.

However, creating the SKA-Mid will interfere with MeerKAT’s observations, says South African Radio Astronomy Observatory director Pontsho Maruping in Cape Town. Radio telescopes are particularly sensitive to radio waves emitted by vehicles and communications equipment. “We’ll do everything we can to make sure feedback isn’t unnecessarily interrupted,” she says. MeerKAT will continue to monitor until it is integrated into SKA-Mid in 2027.

By the end of the year, SKAO, based in the UK, had awarded €500m in construction bids. About 70% of contracts have to go to industry in member states. There are currently eight full members of the organization – Australia, China, Italy, the Netherlands, Portugal, South Africa, Switzerland and the United Kingdom – and France plans to join.

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