64 radio telescopes come together to act as one giant observatory

Located in the northern cape of South Africa, the MeerKAT telescope consists of 64 powerful radio antennas dedicated to investigating the mysteries of the universe. This facility is a precursor to the future Square Kilometer Array Observatory (SKAO), which will consist of MeerKAT and hydrogen age reionization array (HERA) in South Africa, the Australian SKA Pathfinder Observatory (ASKAP) and the Murchison Radio Astronomy Observatory in Australia. The primary goal of SKAO is to understand the content of matter in the universe and the mechanisms driving its evolution and expansion.

The best way to do this is to observe the structure of the universe on the largest scales, where astronomers can observe the distribution of galaxies, the nature of gravity, and the role of dark matter and dark energy. To this end, an international team of astronomers has combined the power of MeetKAT’s 64 radio telescopes to detect faint signals of neutral hydrogen gas across cosmic scales. The resulting accuracy and sensitivity provide evidence of what SKAO can achieve in the near future.

The international team’s findings are described in a recent research paper that appeared online and has been submitted for publication by Monthly Notices of the Royal Astronomical Society. The team was led by Stephen Cunnington of the Jodrell Bank Center for Astrophysics, and included members from the South African Radio Astronomy Observatory (SARAO), the Shanghai Astronomical Observatory, the Istituto Nazionale di Fisica Nucleare (INFN), the Instituto de Astrofísica e Ciências do Espaçol, and the NAOC Center -UKZN for computational astrophysics, multiple research institutes and universities.

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A “Radio Color” view of the sky over the Murchison Widefield Array Radio Telescope. Credit: Natasha Hurley-Walker (ICRAR/Curtin), Team GLEAM; ICRAR / d. John Goldsmith / Heavenly Visions

Radio telescopes are of great value when it comes to cosmology, which is the study of the origin, evolution, and future of the universe. In particular, radio telescopes can detect radiation at wavelengths of 21 cm, which is part of the radio spectrum produced by neutral hydrogen. As the most abundant element in the universe today, analyzing it in three dimensions allows astronomers to map the overall distribution of matter in the universe. It also penetrated the universe a few hundred thousand years after the Big Bang, when the first stars and galaxies were just beginning to form.

Due to the lack of visible light in this period, astronomers know them as the “cosmic dark ages”, which were dissipated about a billion years after the Big Bang by the first galaxies. Thus, studying neutral hydrogen with a wavelength of 21 centimeters will allow astronomers to penetrate the veil of the “dark ages” and first watch the galaxies we observe today coalesce. To accomplish this feat, astronomers need radio antennas that combine tremendous power and sensitivity that can continuously monitor large portions of the night sky over time.

That is the purpose of SKAO, a next-generation group headquartered at Jodrell Bank in Cheshire, England. While still under construction, observatories such as MeerKAT are known as “precursor facilities” that guide SKAO’s design. By integrating 64 arrays in single dish mode, MeerKAT will henceforth act as an interferometer, collecting different arrays of light from distant sources, serving as a single giant telescope that can produce images with much higher resolution. As Cannington explained in a recent University of Manchester release:

However, the interferometer would not be sensitive enough to larger scales that are more interesting to cosmologists studying the universe. Therefore, we are using the array as a group of 64 individual telescopes allowing them to map the giant sky volumes required for cosmology.”

A composite image of SKA combining all the elements in South Africa and Australia. Credit: SKAO

As they note in their paper, the new single dish mode allowed the international team to create radio density maps over a group of galaxies recently studied by the WiggleZ Dark Energy Survey – a survey of galaxies done by the Anglo-Australian Telescope between 2006 and 2011. By combining data , they found a strong statistical correlation between the radio maps and the locations of the scanned galaxies, which demonstrated the ability of MeerKAT to detect the large-scale cosmic structure and track the total matter of the universe.

In addition to being the first case in which such discoveries have been made using a multiplate array (operating as individual telescopes), these results also represent an important milestone in the development of SKAO. As Kennington revealed:

“This discovery was made using only a small amount of pilot survey data. It is encouraging to imagine what will be achieved as MeerKAT continues to make increasingly larger observations. It has been working for many years to predict the future ability of SKAO. To now reach a point where we develop the tools That we need and prove that it works using real data is very exciting. This is only the beginning of what we hope will be an ongoing demonstration of results that advance our understanding of the universe.”

In-depth reading: University of Manchester