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SKA pathfinders provide strongest evidence yet for low-frequency gravitational waves
from Contact 14
BY ANIM VAN WYK (SKAO)
In multiple scientific articles published in June, astronomers detailed the results of decades of observations to spot ripples in spacetime by focusing on extinguished stars called pulsars.
Among the facilities involved were several SKA pathfinders –designated telescopes or systems undertaking SKA-related technology, science, or operations activities:
China’s Five-hundred-meter Aperture Spherical Telescope (FAST)
Radio Telescope Effelsberg in Germany
India’s Giant Metrewave Radio Telescope (GMRT)
CSIRO’s Parkes radio telescope, Murriyang, in Australia
Arecibo Telescope in Puerto Rico, which held SKA pathfinder status until its 2020 collapse.
Westerbork Synthesis Radio Telescope/APERTIF in the Netherlands
Lovell Telescope in the UK, part of the SKA pathfinder eMERLIN
Though scientists using the Laser Interferometer Gravitational-Wave Observatory (LIGO) achieved the first direct observation of gravitational waves in 2015 – about a hundred years after they were first theorised by Albert Einstein – it involved measuring interference in laser beams, not radio waves emanating from pulsars. These waves were then traced to the collision of two stellar-mass black holes 1.3 billion light-years ago.
The most likely origin of low-frequency gravitational waves is the cosmic distribution of binary black-hole systems weighing millions to billions of solar masses, formed when galaxies frequently collided and merged in the early Universe. These lower frequencies cannot be measured by detectors on Earth. The long distance between Earth and pulsars, which lie beyond our Solar System, enables lower frequency waves to be detected.
Senior scientist at the Max Planck Institute for Radio Astronomy and core member of the SKA Pulsars Science Working Group, Dr David Champion, explained: “Pulsars are excellent natural clocks. We use the incredible regularity of their signals to search for tiny changes in their ticking to detect the subtle stretching and squeezing of spacetime by gravitational waves originating from the distant Universe.”
The results are now being pooled through the International Pulsar Timing Array consortium to confirm what would be the first detection of gravitational waves using pulsars. These efforts will expand this emerging area of science, which forms a key SKA science goal.
“The latest findings mark the culmination of decades of effort in precision pulsar timing,” said the SKAO’s Science Director, Dr Robert Braun. “They are a major step towards opening this exciting new window into gravitational wave physics. The SKA telescopes’ contribution to precision pulsar timing will undoubtedly provide new insights, in addition to also allowing individual merger events and late stage in-spirals to be witnessed.”
