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 over vast sites in Australia and Africa – will collect the radio signals emitted by celestial objects, and will hopefully shed light on some of the most enigmatic problems in astronomy, 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 Northern Cape and Western Australia to celebrate the milestone with officials from the SKA Observatory (SKAO), the intergovernmental organization responsible for the telescopes.
“We’re basically setting the foundation for this instrument for the next 50 years,” says Lindsey Magnus, director of the South African-built telescope, which is based in Cape Town, South Africa. “That’s the exciting part — it’s a long-lasting legacy.”
years in the making
In 2012 it was decided that what was initially considered 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 50 MHz and 350 MHz and SKA-Mid will receive frequencies between 350 MHz and 15.4 GHz. Both are interferometers, where many dish-shaped antennas work together as a single telescope.
The SKA will be built in phases, with the €1.3 billion ($1.4 billion) first phase expected to be completed in 2028. Another 700 million euros will be earmarked for the operating costs of the telescopes during the next decade. The ultimate goal is to receive thousands of dishes in South Africa and the partner countries in Africa, and one million antennas in Australia, with a total collection area of one square kilometer. Phase A is about a tenth of the total planned project.
The SKA-Low telescope, in Australia, will include about 131,000 antennas, each of which resembles a two-meter high Christmas tree. More than 500 arrays of 256 antennas will scan the red sands of the site, renamed Inyarrimanha Ilgari Bundara, the CSIRO Murchison Radio Astronomy Observatory. ‘Inyarrimanha Ilgari Bundara’, a name chosen by the traditional owners of the land, the Wajari Yamaji, means ‘sharing sky and stars’.
Earlier this month, the Wajarri Yamaji and the Australian government signed a land use agreement that will allow the telescope to be built on Wajarri Yamaji land. Local people will act as heritage watchers and accompany SKAO officials before any land disturbance during construction, says Des Mongo, a member of the Wajarri Yamatji community who is looking forward to starting work. “Once they’ve started construction, there are opportunities for the Wajari people to be involved in employment and commercial opportunities.”
Scientists are also eager for the antennas to start collecting data. “[SKA-Low’s] “Sensitivity will allow us to observe the distant universe in greater detail than anything we’ve done so far,” says Douglas Bock, 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 billion years.” The firsts of the universe.”
But the most exciting science will be phenomena that “we didn’t even know existed” when the telescopes were designed, predicts Perth-based SKA-Low telescope director Sarah Pearce. The first four arrays will collect data until 2024, with all arrays completed by 2028.
The dishes of South Africa
Preparations for the construction of the first giant sections of SKA-Mid will also begin on Monday. These will form a collection of 197 antennas, spanning about 150 kilometers in the dry Karoo region of South Africa. Four will be completed in 2024, and many more will be added by 2028.
South Africa’s 64-dish MeerKAT telescope is already on site, and will be integrated into SKA-Mid. In early 2022, using MeerKAT data, an international team released the most detailed image yet of the center of our galaxy1, the Milky Way, as well as images of mysterious radio filaments emanating from the galaxy’s black hole. The South African government and the Max Planck company in Germany are adding another 20 plates to the telescope, as part of an expansion project. MeerKAT will be integrated into SKA-Mid only towards the end of its construction in 2027.
“SKA will be a big scientific step forward,” says Erwin de Blok, an astronomer at the Netherlands Institute for Radio Astronomy in Dinglow and principal investigator of MeetKAT’s MHONGOOSE program studying galaxy formation. SKA-Mid “will help us study nearby galaxies in detail and directly identify the gas flow into galaxies and the processes leading to star formation.”
However, construction of SKA-Mid will interfere with MeerKAT observations, says South African Radio Astronomy Observatory director Pontsho Maruping in Cape Town. Radio telescopes are particularly sensitive to the radio waves emitted by vehicles and communication devices. “We’re going to do everything we can to make sure that observations are not unduly interrupted,” she says. MeerKAT will continue observing until it is integrated into SKA-Mid in 2027.
By the end of the year, UK-based SKAO had awarded €500 million in construction tenders. About 70% of the contracts should go to industry in the member states. There are currently eight full members of the organization – namely Australia, China, Italy, the Netherlands, Portugal, South Africa, Switzerland and the United Kingdom – with France planning to join.