John Peacock is a cosmologist who has made significant contributions to our understanding of the cosmic evolution of extragalactic radio sources, or radio galaxies, which actively emit electromagnetic radiation at radio wavelengths. John has also provided insight into how gravitational lensing can be exploited in the mapping of dark matter, and studied the large-scale distribution of galaxies.

He has developed methods for comparing the observed distribution of galaxies on various scales with the expected growth in cold dark matter. In the late 1990s and early 2000s, he led the 2dF Galaxy Redshift Survey, which determined the large-scale structure in one section of the local Universe and demonstrated the constraints on the amount and distribution of dark matter.

John is the author of hundreds of research articles as well as the influential textbook Cosmological Physics (1999). In 2014, he was named a Thomson Reuters Highly Cited Researcher, which ranked him amongst the top 12 astronomers in the United Kingdom. He was awarded the 2014 Shaw Prize in Astronomy.