📋 Tender Overview
A Pulsar Timing Array uses the clock-like predictability of so-called pulsars (pulsating radio stars) to detect faint deviations from their regular behaviour caused by gravitational waves – minuscule ripples in the fabric of spacetime. As an international collaboration of radio astronomers from Australia, Germany, the UK, South Africa, the Netherlands, Italy and France, the MeerKAT Pulsar Timing Array (MPTA) has created a Galaxy-sized gravitational wave detector by monitoring the regular pulses of pulsars with the MeerKAT radio telescope in South Africa to nanosecond precision.
The gravitational waves observed with pulsar timing arrays are caused by some of the universe’s most powerful sources, from supermassive black hole binaries to events just moments after the Big Bang. Matt Miles, a researcher at Swinburne University of Technology in Melbourne, Australia, and one of the leaders of the MeerKAT Pulsar Timing Array data release explains: “Ringing throughout cosmic history, the accumulation of all these waves forms a gravitational wave background, a cosmic hum that provides valuable clues about the hidden processes shaping our universe.”
Creating a map of the gravitational waves across the sky allows searching for areas with an anomalous excess of gravitational radiation, so-called ‘hot spots’, caused by a single, stand-out supermassive black hole binary, promising insights about the gravitational wave background origin. Equipped with the largest number of pulsars jointly used in any such analysis, and profiting from the high-quality data of the MeerKAT radio telescope, a group of researchers led by Kathrin Grunthal, a PhD student at the Max Planck Institute for Radio Astronomy (MPIfR), published the most informative map of the gravitational wave sky. She reflects: “By looking for variations in the gravitational waves across the sky, we hunt for the fingerprint of the astrophysical processes behind the gravitational wave signal.”
While most parts of the sky show no sign of anisotropy, the research team revealed a small number of intriguing features which will be followed up upon in future work. Rowina Nathan, co-author of the Anisotropy paper comments: “Mapping the gravitational-wave background provides us with a more complete picture of the Universe.”
This gravitational wave sky map builds upon the notable evidence of the gravitational wave background signal within the MeerKAT Pulsar Timing Array dataset. “Previous maps have assumed there was no signal present. Now that we have evidence for gravitational waves it changes the mathematics. Ours is the first timing array map to take this into account,” comments MPIfR astronomer David Champion. Compared to similar global PTA efforts such as the European Pulsar Timing Array (who, along with international collaborators, published the first evidence for these low frequency gravitational waves in 2023), the MeerKAT Pulsar Timing array needed just one-third of the observational time span to match their sensitivity.
“This is testament to the outstanding capabilities of the MeerKAT radio telescope, in which our institute has been a leading collaborator, providing hardware, software and scientific work across a whole range of projects,” says MPIfR director Michael Kramer.
The work by the MeerKAT Pulsar Timing Array collaboration represents a significant leap towards the future of gravitational wave research based on radio astronomy. MeerKAT is a precursor for the Square Kilometre Array (SKA) and will eventually be integrated into the SKA Observatory’s SKA-Mid telescope, currently under construction in South Africa. The results from the MeerKAT Pulsar Timing Array collaboration demonstrate the crucial role these next-generation radio telescopes will play in global efforts to explore the low-frequency gravitational wave universe.
