John Bolton and the Nature of Discrete Radio Sources Thesis submitted by Peter Robertson BSc (Hons) Melbourne, MSc Melbourne 2015 for the degree of Doctor of Philosophy in the School of Agricultural, Computational and Environmental Sciences University of Southern Queensland ii Peter Robertson: ‘John Bolton and the Nature of Discrete Radio Sources’ Abstract John Bolton is regarded by many to be the pre-eminent Australian astronomer of his generation. In the late 1940s he and his colleagues discovered the first discrete sources of radio emission. Born in Sheffield in 1922 and educated at Cambridge University, in 1946 Bolton joined the Radiophysics Laboratory in Sydney, part of Australia’s Council for Scientific and Industrial Research. Radio astronomy was then in its infancy. Radio waves from space had been discovered by the American physicist Karl Jansky in 1932, followed by Grote Reber who mapped the emission strength across the sky, but very little was known about the origin or properties of the emission. This thesis will examine how the next major step forward was made by Bolton and colleagues Gordon Stanley and Bruce Slee. In June 1947, observing at the Dover Heights field station, they were able to show that strong radio emission from the Cygnus constellation came from a compact point-like source. By the end of 1947 the group had discovered a further five of these discrete radio sources, or ‘radio stars’ as they were known, revealing a new class of previously-unknown astronomical objects. By early 1949 the Dover Heights group had measured celestial positions for the sources accurately enough to identify three of them with known optical objects. One coincided with an unusual object in the local Galaxy and two coincided with peculiar extragalactic objects. As I will show, the optical identifications built a bridge between traditional astronomy and the fledgling radio astronomy. The identifications also marked the birth of extragalactic radio astronomy, which was to have a major impact on the development of astronomy in the second half of the twentieth century. In the early 1950s, with improved instrumentation, the Dover Heights group carried out a sky survey that revealed over 100 radio sources, consolidating its position as the world’s leading group for ‘cosmic’ radio astronomy. To conclude, I will briefly survey Bolton’s career after the closure of Dover Heights in 1954. Bolton had the unusual distinction of being the inaugural director of two major observatories, first at the California Institute of Technology (1955–60) and then at the Parkes Observatory (1961–81) in central NSW. No astronomer did more over his career to establish radio astronomy as a mature and powerful branch of astronomy. Peter Robertson: ‘John Bolton and the Nature of Discrete Radio Sources’ iii iv Peter Robertson: ‘John Bolton and the Nature of Discrete Radio Sources’ Certification of Dissertation I hereby certify that the work contained in this dissertation is the bonafide work of my own, that the work has not been previously submitted for an award, and that, to the best of my knowledge and belief, the dissertation contains no material previously published or written by another person except where due acknowledgement and reference is made in the dissertation to that work. __________________________________ _________________ Signature of Candidate Date ENDORSEMENT ___________________________________ __________________ Signature of Principal Supervisor Date ____________________________________ __________________ Signature of Associate Supervisor Date Peter Robertson: ‘John Bolton and the Nature of Discrete Radio Sources’ v vi Peter Robertson: ‘John Bolton and the Nature of Discrete Radio Sources’ Acknowledgments This PhD began as a part-time off-campus project at James Cook University in 2008. In 2013 my PhD was transferred to the School of Agricultural, Computational and Environmental Sciences at the University of Southern Queensland. I would like to thank my supervisors at JCU, Professor Wayne Orchiston, Dr Bruce Slee and Professor Richard Strom, and my supervisors at USQ, Professor Brad Carter and Professor Wayne Orchiston, for their guidance and support. The research for this thesis has been carried out in conjunction with the preparation of a full-length biography of John Bolton to be published as a book. I would especially like to thank Mrs Letty Bolton and Professor Ron Ekers for their continued support of this project. My research has drawn on three principal sources of archival material: the personal papers of John Bolton held in the National Library of Australia (Canberra); the official correspondence files of the Radiophysics Lab held in the National Archives of Australia (Chester Hill, NSW); and the Radio Astronomy Image Archive administered by the Australia Telescope National Facility (Marsfield, NSW). I am grateful to the staff at these three institutions for their assistance in accessing this material. I would like to thank the National Library of Australia for providing a Harold White Fellowship to support my study of the Bolton papers in 2008 and to Manning Clark House in Canberra for providing a Residential Fellowship in 2009. I am also grateful to three Examiners for their helpful and constructive comments on an earlier draft. Their comments have resulted in a significant improvement to the historical accuracy and interpretation of this final version. Finally, I am pleased to dedicate this thesis to my amazing, talented daughters, Katie and Laura. Peter Robertson: ‘John Bolton and the Nature of Discrete Radio Sources’ vii viii Peter Robertson: ‘John Bolton and the Nature of Discrete Radio Sources’ Table of Contents Abstract iii Certification Page v Acknowledgments vii Chapter 1 Introduction 1 1.1 Literature Review 1 1.2 Discussion of Unpublished Sources 3 1.3 Summary of Chapters 6 Chapter 2 From Radar to Radio Astronomy 11 2.1 Early Life: From Sheffield to Sydney 12 2.2 Origins of the Radiophysics Laboratory 25 2.3 A Mysterious Cosmic Hiss: Karl Jansky and Grote Reber 32 Notes to Chapter 2 39 Chapter 3 Discovery of the First ‘Radio Stars’ 43 3.1 The Beginning of Radio Astronomy in Australia 43 3.2 Cygnus A: The First Discrete Radio Source 53 3.3 A New Class of Astronomical Objects 66 Notes to Chapter 3 70 Chapter 4 Identification of the First Radio Sources 75 4.1 The Expedition to New Zealand 77 4.2 Analysis of the New Zealand Data 87 4.3 Optical Identifications of the First Three Sources 91 Notes to Chapter 4 100 Chapter 5 Emergence of Radio Astronomy in Australia & England 105 5.1 Transition of CSIR to CSIRO 106 5.2 Postwar Growth of the Radiophysics Lab 110 5.3 A Rather Distant Outpost: The Radiophysics and Cavendish Labs 115 5.4 A Tour of Radio Astronomy Centres 126 Notes to Chapter 5 143 Peter Robertson: ‘John Bolton and the Nature of Discrete Radio Sources’ ix Chapter 6 Consolidation and Competition: Dover Heights 1951–54 149 6.1 Cygnus A Revisited: Galaxies in Collision? 153 6.2 Coming of Age – The 1952 URSI Congress in Sydney 163 6.3 A Hole-in-the-Ground: Discovery of the Galactic Nucleus 171 6.4 The Struggle for Resources: The Final Years at Dover Heights 182 Notes to Chapter 6 194 Chapter 7 An Overview of John Bolton’s Career 1955–81 199 7.1 High in the Sierras – The Owens Valley Radio Observatory 202 7.2 Receding Horizons – The Discovery of Quasars 210 7.3 An Australian Icon – The Parkes Radio Telescope 220 Notes to Chapter 7 229 Chapter 8 Concluding Remarks 231 Bibliography 241 List of Tables and Figures [A] Short titles and page numbers 247 [B] Sources of tables and images 249 Appendix: Dover Heights Bibliography [A] Papers by Dover Heights group in chronological order 1947–57 251 [B] Most cited papers by the Dover Heights group 252 x Peter Robertson: ‘John Bolton and the Nature of Discrete Radio Sources’ Chapter 1 Introduction John Bolton is regarded by many to be the pre-eminent Australian astronomer of his generation. His career consisted of three distinct periods: the years 1946–53 at the Dover Heights field station in Sydney; the years 1955–60 at the California Institute of Technology (Caltech) in Pasadena; and the years 1961–81 at the Parkes telescope in central New South Wales. This thesis will focus almost entirely on the Dover Heights period. It was during this time that Bolton, together with colleagues Gordon Stanley and Bruce Slee, discovered and identified the first discrete radio sources, or radio ‘stars’ as they were known, one of the most important discoveries in twentieth century astronomy. The research for this thesis has been carried out in parallel with the first full-length biography of Bolton, which is currently in preparation. The Dover Heights period will be covered in three chapters of the biography. The thesis will be a far more detailed and rigorous study of this period than is possible in the book. In the present chapter, we will review the relevant published sources, discuss the unpublished sources, and conclude with a brief outline of each of the other seven chapters. 1.1 Literature Review The origins and early development of radio astronomy in Australia is possibly the most intensively-studied chapter in the history of Australian science. Radio astronomy began immediately after the end of World War II in the Radiophysics Laboratory in Sydney, a division of the Council for Scientific and Industrial Research (the forerunner of the Commonwealth Scientific and Industrial Research Organisation – CSIRO). In the late 1940s and early 1950s the Radiophysics Lab operated up to eight field stations in and around Sydney. The radio observations at each site were under the general supervision of the head of the radio astronomy group, Joseph Lade Pawsey (1908–62). The early radio observations at a number of these field stations have been the focus of two recent PhD theses.