All  
Radio Telescope

Powerful Radio Telescopes in South Africa are Revolutionizing Astronomy

Print

The world’s largest radio telescope is expected to come online sometime in 2020. The S quare Kilometre Array (SKA) is an internationally sponsored and funded initiative that will include more than one million square metres of collecting area when all of its installations are complete.

With thousands of individual dishes and approximately one million low-frequency antennas at their disposal, astronomers will be able to survey the sky above the Earth in exquisite and comprehensive detail. Despite being based on our planet’s surface, SKA image resolution quality will actually exceed that of the Hubble Space Telescope.

One unique aspect of the project is that it will incorporate dishes on two separate continents in the Southern hemisphere. SKA facilities in secluded desert regions of South Africa and Australia will work in coordination to supply scientists with a far more panoramic view of the sky than was previously attainable. Sky scanning speed will exceed previous standards by an impressive factor of 10,000, and the array’s sensitivity will be 50 times greater than what radio telescopes have achieved before.

The Karoo Array Telescope and the Beginning of a New Era

In South Africa, the precursor to the SKA project was a radio telescope called the Karoo Array Telescope, named in honor of the desert region where it sits. Before being absorbed into the larger MeerKAT project, which represents the bulk of South Africa’s contribution to the SKA system, the KAT-7 offered a preview of coming attractions and helped contribute to the advancement of radio astronomy in its own right.

In 2013, just a year after it went into operation, the Karoo Array Telescope produced its first notable results. In an announcement published in the Monthly Notices of the Royal Astronomical Society , a team of international scientists, including astronomers from the University of Southampton, revealed their discovery of massive ejections of stellar matter from a binary star system located 30,000 light-years from Earth. 

What was observed was a neutron star system called Circinus X-1. This is a two-star system, in which both stars orbit each other in an elliptical formation. One of these is a high-density compact neutron star, which is a remnant of a much larger star that exploded and then collapsed in on itself. This star would likely be no more than 20 kilometres in diameter, making it appear as an insignificant dot next to its much larger companion.

But with neutron stars, looks are deceiving. Their gravitational pull is that of a much larger object, and when the two stars in Circinus X-1 come close the super-dense neutron star rips out humongous clouds of material from its partner. This creates massive jet-like flares of stellar material that are highly energized and only identifiable on Earth from the radio waves they produce.

“The dramatic radio flares happen when the matter Circinus X-1 has violently ejected slows down as it smashes into the surrounding medium,” explained Dr. Richard Armstrong, an SKA expert from the University of Cape Town. "These types of observations are crucial for understanding the processes of both accretion of matter onto extremely dense systems, such as neutron stars and black holes of both about the sun's mass, and also the so-called supermassive variety we now know to be at the centre of most galaxies."

Such events were not easy to discover before. But the brand new composite antenna structure of the KAT-7 opened new opportunities for astronomers to explore remarkable and important phenomena occurring at incredible distances.

“It provides a unique glimpse of the laws of physics operating in extraordinary regimes,” said astronomy professor Rob Fender from the University of Southampton, in reference to both the KAT-7 telescope and the greater MeerKAT project into which it has now been absorbed. “Nearly all such events are associated with transient radio emission. By studying bursts from these phenomena, we can pinpoint the sources of explosive events.”

MeerKAT Opens for Business

The KAT-7 was the centerpiece of the South African SKA project until July 2018, when the crown jewel MeerKAT radio telescope was declared ready and fit for duty . This 64-dish, eight-kilometre installation, which is located near the town of Carnarvon in the desolate Karoo region, was introduced to scientists, government officials and the public at large during a special inauguration ceremony.

“MeerKAT will address some of the key science questions in modern astrophysics—how did galaxies form, how are they evolving, how did we come to be here,” proclaimed Fernando Camilo from the South African Radio Astronomy Observatory. “For those purposes MeerKAT is the best in the world.”

It didn’t take long for the MeerKAT to produce results backing that statement. Even before it was officially brought online it was already collecting data, and at the inaugural event attendees were treated to spectacular images taken of the centre of our galaxy, 25,000 light-years away, where a massive black hole holds the rest of the Milky Way in its iron grip.

“We didn’t expect to use our telescope so early in the game,” said Camila. “But to turn it to the centre of the galaxy and obtain these stunning images, the best in the world, tells you you’ve done something right.”

Just one year later, on July 22, 2019, the MeerKAT struck again. It solved a mystery that had puzzled astrophysicists for quite some time, when it revealed the presence of colossal clouds of hydrogen gas in a mega-galaxy known as NGC 1316 . This sprawling galaxy is located 60 million light-years away and was created by the collision of two smaller galaxies plus the absorption of several nearby satellite galaxies.

This scenario of collision and merger has been identified as a key producer of galaxies throughout the universe. But the presence of hydrogen was never detected in NGC 1316 before, putting the story of its origin scientists had concocted in doubt.

But when the MeerKAT was trained on NGC 1316, it quickly found the elusive hydrogen clouds. Through the intervention of tidal forces they’d been stretched thin and pulled into elongated tails, where they were obscured by the blinding visual field created by star clusters that had been shaped by the same forces.

Just like that, a quandry that had confused astronomers was solved and a popular theory of galaxy formation was confirmed—all thanks to MeerKAT.

“The amount of gas found is consistent with that expected based on merger theory,” explained Paolo Serra, an Italian astronomer involved in the data analysis. “Thus, thanks to these observations all pieces of the puzzle are now in place, and we finally have a more precise and coherent understanding of the formation of this famous galaxy.”

Fernando Camilo echoed this praise of the MeerKAT’s advanced capabilities.

“This provides a wonderful taste of what MeerKAT will do in the years to come,” he said. “Results like these show that MeerKAT has begun addressing some of the key open questions in modern astrophysics, and we look forward to researchers in South Africa and from around the world joining us on a journey of scientific discovery.”

South African Radio Astronomy on the March

Once the entire Square Kilometre Array becomes operational next year, astronomical researchers everywhere will have access to an extraordinary and expansive database of information. The SKA project will revolutionize the practice of radio astronomy and dramatically increase our depth of knowledge about how stellar and galactic evolution unfold.

In coordination with their partners in Australia, the South African Radio Astronomy Observatory will have an opportunity to make history. Their involvement with the SKA project will elevate their international profile and make their country one of the planet’s major hubs for 21 st century ground-based space exploration.

Top image: Radio Telescopes observe the sky. Credit: vchalup / Adobe Stock

By Nathan Falde

 

Next article