Observations of 80 millisecond pulsars (shown as bright point sources emitting white radio beams) over the past five years with MeerKAT have revealed evidence for a gravitational wave background. Photo: Carl Knox, OzGrav, Swinburne University of Technology and South African Radio Astronomy Observatory.
Harnessing the extraordinary capabilities of South Africa’s world-renowned MeerKAT radio telescope, compelling evidence has been discovered for a low-frequency gravitational wave background.
The University of Cape Town (UCT), in collaboration with the South African Radio Astronomy Observatory (SARAO) and leading international institutions, made the groundbreaking stride in unveiling the mysteries of the universe.
The MeerKAT Pulsar Timing Array project, a five-year initiative that began in 2019, utilises the precision of pulsars – rapidly spinning neutron stars – as natural cosmic clocks.
These celestial bodies, located thousands of light-years away, act as the largest galactic gravitational wave detector of its kind, leading to the most detailed gravitational wave maps created.
“To find evidence for a gravitational wave background, we first need to model the timing behaviour of each of the pulsars in our network very precisely,” said Dr Marisa Geyer, co-author and lecturer at UCT and former commissioning scientist of MeerKAT.
“Once we know the individual pulsars well, we can start analysing the combined behaviour of the group of pulsars.
“If we see pulsars in the same direction in the sky lose time in a connected way, we start suspecting that it is not the pulsars that are acting funny, but rather a gravitational wave background that has interfered.”
The findings, published in the Monthly Notices of the Royal Astronomical Society, represent a collaboration amongst international partners from UCT, Australia, Europe and SARAO.
The results offer unprecedented insights into the likely sources of these spacetime ripples – primarily the colossal mergers of supermassive black holes.
UCT postdoctoral fellow, Dr Jaikhomba Singha, said: “Pulsar timing array experiments are long-term in nature and searching for a gravitational wave background is a slow process. From past experience, we know that this may need 15 years of data. It is amazing to see that with MeerKAT evidence for the signal is possible even in a data-span of just 4.5 years.”
This research lays the foundation for deeper exploration into the evolution of galaxies and the formation of supermassive black holes.
The upcoming SKA-Mid telescope, incorporating MeerKAT and currently under construction in the Karoo, promises to expand these discoveries even further, positioning South Africa at the forefront of the next generation of cosmic exploration.
“It is a wonderful time to work in the field of gravitational waves using pulsar timing experiments,” said UCT PhD student Atiqur Rahman.
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