Professor George Efstathiou has been awarded the Shaw Prize in Astronomy, one of the biggest prizes in the field.
Efstathiou, Emeritus Professor of Astrophysics (1909) at Cambridge's Institute of Astronomy, shares the prize with Professor John Richard Bond from the Canadian Institute for Theoretical Astrophysics and the University of Toronto.
They were recognised for their pioneering research in cosmology, in particular for their studies of fluctuations in the cosmic microwave background. Their predictions have been verified by an armada of ground-, balloon- and space-based instruments, leading to precise determinations of the age, geometry, and mass-energy content of the universe.
Cosmology has undergone a revolution in the past two decades, driven mainly by increasingly precise measurements of the angular power spectrum of fluctuations in the temperature and polarisation fields of the cosmic microwave background, a relic of the early universe, most notably by NASA's Wilkinson Microwave Anisotropy Probe spacecraft (2001-2010) and the European Space Agency's Planck spacecraft (2009-2013).
These fluctuations are small - the strength of the background radiation is the same in all directions to better than 0.01% and it is only slightly polarised - but they offer a glimpse of the universe when it was very young, a test of many aspects of fundamental physics, insights into the nature of dark matter and dark energy, and measurements of many fundamental cosmological parameters with accuracies unimaginable to cosmologists a few decades ago.
Although many researchers contributed to the development of the theoretical framework that governs the behaviour of the cosmic microwave background, Bond and Efstathiou emphasised the importance of the background as a cosmological probe and took the crucial step of making precise predictions for what can be learned from specific models of the history and the composition of the mass and energy in the universe.
Modern numerical codes used to interpret the experimental results are based almost entirely on the physics developed by Bond and Efstathiou. Their work exemplifies one of the rare cases in astrophysics where later experimental studies accurately confirmed unambiguous, powerful theoretical predictions.
The interpretation of these experiments through Bond and Efstathiou's theoretical models shows that the spatial geometry of the observable universe is nearly flat, and yields the age of the universe with a precision of 0.15%, the rate of expansion of the universe with a precision of 0.5%, the fraction of the critical density arising from dark energy to better than 1%, and so on. The measurements also strongly constrain theories of the early universe that might have provided the initial "seed" for all the cosmic structure we see today, and the nature of the dark matter and dark energy that dominate the mass-energy content of the universe.
Both Bond and Efstathiou have worked closely with experimentalists to bring their predictions to the test: they have been heavily involved in the analysis of cosmic microwave background data arising from a wide variety of experiments of growing sophistication and accuracy.
George Efstathiou received his BA in Physics from the University of Oxford and PhD in Astronomy from Durham University. He has held postdoctoral fellowships at the University of California, Berkeley, USA and the University of Cambridge. He was Savilian Professor of Astrophysics at Oxford, where he served as Head of Astrophysics until 1994. He returned to Cambridge in 1997 as Professor of Astrophysics, where he also served as Director of the Institute of Astronomy and the first Director of the Kavli Institute for Cosmology. He received the 2022 Gold Medal of the Royal Astronomical Society. He is a Fellow of the Royal Society of London and the Royal Astronomical Society, UK. He is a Fellow of King's College, Cambridge.
