Hanbury Brown Obituary 2002

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Obituary depended on correlating light quanta, or photons. In essence, it required photons to Robert Hanbury Brown (1916–2002) arrive in pairs: astronomers thought they might; some physicists said they could not. At the same time as the Hanbury Brown–Twiss equation demonstrated the feasibility of pair-arrival, Hanbury’s wife Heather symbolically produced twin sons. In a major astronomical ‘first’, Hanbury

HANBURY BROWN FAMILY BROWN HANBURY demonstrated the feasibility of his intensity interferometer by measuring the diameter of the ‘dog star’, Sirius, under the unusually favourable sky conditions of the harsh British winter of 1955–56. He then sought Pioneer in radar and observational astronomy more interesting stars in the Southern Hemisphere, under less cloudy skies. So Robert Hanbury Brown, a giant from a until then, had been thought to be the he left his personal chair at Manchester, golden period of innovation in astronomy, origin of all such emissions. and moved to the University of Sydney in died on 16 January this year, at the age of 85. This discovery, using a fixed paraboloid 1962, joining the extraordinary physics Hanbury, as he was always known, was dish, was the happy retort to those department being put together there by born in India in 1916, the son of an army questioning the feasibility of the huge Harry Messel. This was the first really officer. Forsaking his schoolboy plans to steerable radio telescope B.L. was then multi-professorial department in Australia become a classics scholar, he graduated in evangelizing for. Following years of (one of us — R.M. — being there at this engineering from the University of London struggle, this pioneering 250-ft, steerable time as a young faculty member). in 1935. He then worked on the secret dish was completed in 1957. Hanbury was Hanbury’s next interferometer was development of the coastal radar — Chain among those to use it. In particular, he and built in a sheep paddock, outside Narrabri, Home — which was to prove vital in the Hazard played a significant part in the New South Wales. Each of its two telescopes 1940 Battle of Britain. By then, Hanbury discovery of quasars — ‘quasi-stellar was 23 ft in diameter and composed of 250 was working with a group developing a objects’, now taken to be the most distant, mirrors, and they moved on a track 600 ft shorter-wavelength radar that could be and so oldest, observable objects in the in diameter. The local wildlife of the installed in aircraft. His splendid Universe. outback provided both diversion and autobiography, Boffin (Adam Hilger, Early on, Hanbury had also begun to disruption. And drought and flood were 1991), gives a vivid account of the trials think about a radio interferometer, which a feature of the area. Nonetheless, the and triumphs of this work, which by 1941 could measure the angular size of the sky’s interferometer was a winner, with the gave night fighters of the Royal Air Force two strongest radio sources, Cygnus A and diameter of tens of stars being measured, the edge over the German bombers. Cassiopeia A. For all anyone knew, this and a new scale of stellar temperatures Hanbury’s contributions also included might have required an interferometer being established. work on the polarization of radio waves, baseline of a thousand kilometres or more. During these years, Hanbury and his crucial for the optimal design of aerials on The technical difficulty lay in combining family shuttled between Narrabri and his equipment for air-to-surface surveillance the radio signals, received at two widely home at Forty Baskets Beach, with its and in the detection of ships and separated points, with the required splendid view of Sydney harbour. Much of submarines. During his secondment phase stability. Hanbury had the idea the shuttling was done in his beloved Alvis (1942–47) to the US Naval Research of measuring the correlation of the 1952 drophead coupé: given his driving Laboratory in Washington DC, his work fluctuations in intensity, a process that style, the ride down the potentially led directly to the NATO ‘identification does not require the phase information lethal 1-in-4 drive to this house was friend or foe’ (IFF) system of today, along needed in approaches based on detecting unforgettable. Hanbury loved the warmth with the civilian system of ground-based signal amplitudes. This deceptively simple of Australia, and it reciprocated. He was air-traffic control now used throughout solution raises profound questions, and an early recipient of its highest honour, the world. Hanbury collaborated with the theoretical Companion of the Order of Australia But all this was a prelude. Returning physicist Richard Twiss to put it all on a (the order is a cheerfully confused to Britain, Hanbury sought to pursue a sound basis. Surprisingly quickly, by 1952 manifestation of Oz republicanism from higher degree in university research. His the intensity interferometer was built, and the 1970s, the Queen being its head). work having been secret, however, he had had shown the radio sources to be so Five years after his retirement in 1981, no publications. His enquiries brought extended that baselines of only a few he and his wife returned to Britain, and him together with one of us (B.L.), who kilometres were needed (so that earlier lived quietly in Hampshire. Hanbury had returned to the University of methods would have been adequate). was a superb and imaginative Manchester with military radar equipment In Hanbury’s words, he had built a engineer, a natural astronomer, and a and built a 218-ft radio telescope at Jodrell sledgehammer to crack a nut. true visionary. He was also, as we and Bank. Finding ways to minimize the What came next ensured that so many others can attest, a really background noise that bedevilled early Hanbury’s name will always be in lovely man. Bernard Lovell and Robert M. May efforts, Hanbury and his student Cyril astronomy texts. He and Twiss applied Bernard Lovell is at The Quinta, Swettenham, Hazard showed that cosmic radio waves the same ideas to optical astronomy, but Congleton, Cheshire CW12 2LD, UK. were emanating from the Andromeda immediately encountered objections that Robert M. May is in the Department of Zoology, spiral galaxy, 2 million light years away their proposals violated basic physical University of Oxford, Oxford OX1 3PS, UK. and far outside our own Galaxy — which, laws. The experimental approach e-mail: [email protected]