John Gatenby Bolton (5 June 1922 – 6 July 1993) was a British-Australian astronomer who was fundamental to the development of radio astronomy. In particular, Bolton was integral in establishing that discrete radio sources were either galaxies or the remnants of supernovae, rather than stars. He also played a significant role in the discovery of quasars and the centre of the Milky Way. Bolton served as the inaugural director of the Parkes radio telescope in Australia and established the Owens Valley Radio Observatory in California. Bolton's students held directorships at most of the radio observatories in the world and one was a Nobel Prize winner. Bolton is considered a key figure in the development of astronomy in Australia.
Early life John Gatenby Bolton was born in Sheffield, United Kingdom, in 1922 to two high school teachers. While suffering from various sicknesses in his youth, such as severe asthma and migraines, Bolton showed an early interest and proficiency in sports, mathematics, and science. He was awarded a scholarship to the secondary King Edward VII School, but his family was required to pay full fees since his father's salary was above the threshold of the means-tested scholarship. At King Edward VII School, he was elected prefect and was awarded the school's mathematics prize in his final year. His upbringing is considered middle-class for the 1920s and 1930s United Kingdom. Bolton was awarded a place to study pure mathematics and natural philosophy at Trinity College, Cambridge in 1940, and two scholarships to cover his fees and living expenses. Due to World War 2, his degree was reduced from three to two years. In his second year, Bolton decided to focus on physics rather than mathematics. He completed his degree in May 1942 with second-class honours. While an average result for a student that had previously finished in top third of his cohort, his mother had deteriorated and died during Bolton's examination period.
World War 2 and radar work Bolton enlisted with the military after completing his final examinations, and chose the Navy due to his love of ships. He was commissioned as a sub-lieutenant in the Royal Navy Volunteer Reserve. While at officer training at HMNB Portsmouth he chose to do research and development of airborne radar. Bolton's experience of radar during World War 2 would establish key relationships and experiences that would heavily influence his future radio astronomy career. Bolton's first war posting saw him responsible for two coastal radar stations and testing the latest radar sets in night fighters. At the end of 1942, Bolton was transferred to the Telecommunications Research Establishment, the headquarters of Britain's wartime radar research and development. At this location he met many of what would be many of the leaders of the post-war radio astronomy efforts, including Martin Ryle. At the Telecommunications Research Establishment, Bolton first worked on developing a new airborne radar system operating at a wavelength of 3 cm, which included extensive testing during flights. By the time of the D-day landing, Bolton had grown tired of inflight testing radar. He was offered a position as radio officer on the British light aircraft carrier HMS Unicorn. Such a position made Bolton responsible for all airborne electronics, ship-to-aircraft communications, and navigational aids. As a support ship, Unicorn had a reasonably safe war experience, with no major damage reported. Bolton's experience on Unicorn is credited with developing his hands-on expertise with electronics and the ideas that would help him later to build a sea-cliff interferometer. As World War 2 ended in 1945, HMS Unicorn shuttled cargo and personnel in the Pacific theatre back to Australia. When Unicorn returned to Britain in December 1945, Bolton decided to remain in Sydney. The choice to make Australia his new home was largely due to the positive influence the climate had on his health but also because his application to enrol in postgraduate studies at the Cavendish Laboratory at Cambridge University had been rejected. His abbreviated wartime undergraduate degree was deemed inadequate training for postgraduate study by the head of the Cavendish Laboratory, Lawrence Bragg.
CSIR, Cygnus, and the sea-cliff interferometer After leaving the Navy, Bolton searched for a job through his Navy connections in Australia. Through one government official associated with finding work for veterans, an appointment was made for Bolton to meet Taffy Bowen, the head of Radiophysics Laboratory of CSIR. Bolton was soon appointed to the new research officer position, with duties of `research and development in connection with the application of radar techniques'. The expertise in radar technology by the Radiophysics Laboratory was world-class at the time, largely because Britain had shared the secret of radar with its Dominions as World War 2 began and due to a relatively large Australian radio physics community that had intimate ties with the ionospheric physicists in England. Bolton was first assigned to measure the polarisation properties of sunspot radiations, an area of active investigation as the Sun was recently confirmed to be radio bright during World War 2. Bolton built two Yagi antennas and installed them at Dover Heights, Sydney. However, the Sun had entered a dormant period, with no sunspots on its surface. Having learnt of the discovery of radio emission from the plane of the Milky Way during his time at Cambridge University, and from observations onboard HMS Unicorn, Bolton speculated that there might be other radio bright stars like the Sun.
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