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This information will enhance our ability to detect and characterise the cosmic gravitational wave background, a key prediction of Einstein’s Theory of General Relativity.

University of Galway astronomers along with collaborators in the European Pulsar Timing Array consortium have just published in the journal Astronomy & Astrophysics the most in-depth study yet of how the solar wind affects the perfect clock-like beat of radio pulses detected from distant pulsars. Understanding how the space weather associated with the Sun distorts these time signals is critical in being able to detect the subtle underlying variations in space-time associated with the cosmic gravitational wave background.

These waves permeate the cosmos and are believed to originate from innumerable supermassive black hole binary systems in the centres of distant galaxies, stirring up ripples in space-time as they orbit one another, which spread away like waves on a pond, flexing and bending space and time as they wash over us day and night.

These distortions are so unimaginably small they don’t affect us or our daily lives. The only way to detect and study them is to use the Galaxy as a laboratory bench and the collapsed remnants of exploding stars called pulsars scattered nearby us. These pulsars – collapsed stars the size of Galway Bay – spin tens to hundreds of times a second with a precision better than the best atomic clocks, yielding lighthouse beams of radio emission whose beats are easily detected with radio telescopes.

By combining the observations of radio telescopes across the world, astronomers can analyse individual pulsar pulse streams to identify the subtle signatures of underlying gravitational wave ripples. To do that requires understanding and removing the effects of ‘static’ in the form of the tenuous plasma that is present in deep space, but also the plasma constantly radiated away from the Sun, also known as the solar wind. The latter has always been a particular problem given the variability of ‘space weather’ around our nearest star.

However, new work by Sai Chaitanya Susarla, an astronomy PhD researcher in University of Galway’s School of Natural Sciences Physics Unit, has yielded a methodology that can limit the distortions to these pulsar signals caused by the Sun’s ambient plasma, significantly improving our ability to detect and characterise the cosmic gravitational wave background, by studying the clock patterns of several radio pulsars that pass by the Sun on its annual journey on the ecliptic plane along the Zodiac. 

Sai Chaitanya Susarla said: “I am very happy to see this work finally published, it formed the basis of my doctoral studies here at the University of Galway and will be incredibly valuable for the scientific community in being able detect and characterise gravitational waves using pulsar timing arrays. It is also demonstrating a way to use radio observations of pulsars to remotely study the Sun’s environment, which may be very useful for other scientists in trying to understand the basis of space weather and its impact on our home planet”

Dr Aaron Golden, School of Natural Sciences, College of Science and Engineering, University of Galway and Sai Chaitanya Susarla’s co-PhD supervisor, said: “This is a tremendous result for Sai and for the School of Natural Sciences, highlighting the huge impact our young researchers are making in the fundamental sciences, as well as in rethinking what we mean by our ‘planetary health’ from a solar system perspective. Sai’s work provides a new means of monitoring our Sun and to identify how solar storms form and evolve - this will add to our understanding on how the most powerful of such storms affect our planet.” 

University of Galway alumnus Professor Evan Keane, Associate Professor of Radio Astronomy in Trinity College Dublin’s School of Physics, Head of the Irish LOFAR Telescope and co-PhD supervisor, added: “This is an excellent example of how low frequency radio astronomy using facilities such as the I-LOFAR telescope in Birr can contribute to basic and applied scientific research - not only do we have a more precise means of understanding the cosmos at the most fundamental level, but also a new technique that could ultimately contribute towards an ‘early warning’ system for space weather. Auroras are pretty to look at, but really powerful displays are associated with colossal ground induced currents that can shred power infrastructure. Hopefully Sai’s work can help build a better picture of what the warning signs of such events might be.” 

Read the full paper here; published in the professional research journal Astronomy & Astrophysics.