green light for the construction of the world’s largest radio telescope

The telescope – which is being built partly in South Africa and partly in Australia – will soon include nearly 200 dishes and more than 130,000 antennas.

After years of preparation – during which much thought was given to what the ultimate radio telescope should look like and the necessary technologies have already been tested and developed – the decision was made last week. Construction is underway on the Square kilometer table (in short: SKA): the largest radio telescope on Earth.

Jubilation
The decision sent radio astronomers into a jubilant mood. And also Professor Philip Diamond, Director General of the Organization of the square kilometer network (SKAO), couldn’t believe his luck. “I am ecstatic. We have been working on this moment for 30 years. And today an important milestone has been taken (…) we will be building not one, but two of the largest and most complex radio telescope arrays here on Earth, designed to reveal some of our universe’s most fascinating secrets. . The news was also greeted enthusiastically in the Netherlands (one of the SKAO member states, see box). “We are extremely happy to hear that the construction of SKA is finally starting,” said Michiel van Haarlem, Dutch SKA office manager.

The Square Kilometer Array is an intergovernmental project in which 16 countries – including the Netherlands – have been working for years. The countries will pay and build the radio telescope together. The Netherlands is investing around 39 million in SKA and will also supply various components. Its construction is directed by ASTRON, the Dutch Institute for Radio Astronomy.

Bigger and more sensitive
There are of course many radio telescopes available around the world. But the Square Kilometer Array is clearly different from that, says Van Haarlem Scientias.nl. “SKA is larger and therefore more sensitive than existing instruments and can therefore look deeper into the universe (and further in time).”

The huge radio telescope actually consists of two parts. A part goes up in Australia and consists of 131,072 antennas. The other part is in South Africa and has 197 satellite dishes. “Antennas and dishes pick up radio waves, which are then converted into digital signals which are then processed in very fast (super) computers. The end result is, for example, images of the sky at radio wavelengths and other processed signals that can be used to study stars and planets.

Interferometers
The two telescopes in Australia and South Africa operate separately from each other. “One (in Australia) on the longer wavelengths and the one in South Africa on slightly shorter wavelengths,” Van Haarlem explains. “Both are examples of interferometers.” This means that the observations made simultaneously by the nearly 200 dishes in South Africa are merged. The same goes for the sightings of the thousands of antennas in Australia. It actually simulates a huge radio telescope with a total reception area of ​​almost a square kilometer.

Expectations
Expectations are high, as it turns out when we ask Van Haarlem what SKA can find out. “The SKA is a widely applicable instrument with which many investigations can be conducted. From studying the first stars and galaxies in the early Universe, to mapping the distribution of hydrogen gas in near and far galaxies, to looking for pulsars (remnants of ancient stars that emit pulses of radiation radio). Too many to mention. “

The location of the antennas (visible on this artistic impression) and the satellite dishes has been well thought out. A conscious choice was made for the remote areas of Australia and South Africa. “Far from the parasitic signals generated by humans,” Van Haarlem explains. “Elsewhere on Earth, human activity hinders the most sensitive observations. Image: SKAO / ICRAR.

patience
Radio astronomers are eager to examine the first images of the Square Kilometer Array, but it takes patience. Although it has been officially decided to start construction, it will still be some time before the excavator really digs into the ground. It is expected that there will only be some activity at the selected sites in Australia and South Africa at the start of 2022. As this approaches, Member States are not standing still; they are going to prepare for the construction of “their” rooms. “In the coming months, Dutch companies will receive orders for the supply of software and hardware necessary for Square kilometer table be completed by the end of this decade, ”says Van Haarlem.

First observations
As it seems now, it is Square kilometer table stop in 2028. Fortunately, however, the first observations are not long in coming. “A telescope like the SKA is built in stages. Observations can begin before all antennas and dishes have been placed. We expect the first results from 2024.

The construction and use of the largest radio telescope in the world represents around 2 billion euros. “That’s a lot of money, and that’s why 16 countries are working together to build this telescope. We share the costs and thus have access to a more sensitive telescope than each country could have afforded on its own, ”explains Van Haarlem. “And the technological innovation required to build such a complex instrument creates opportunities for companies in participating countries.” But the hearts of radio astronomers naturally beat faster at the idea of ​​SKA because of the fundamental questions the powerful radio telescope can help answer. “Like: how did stars and galaxies come about? What will happen to the universe in the distant future? Is there intelligent life elsewhere on other planets? These are all questions that astronomy, and therefore also the SKA, wants to answer.