Sir Antony Hewish obituary | astronomy
In 1967, a team led by radio astronomer Antony Hewish, who died at the age of 97, discovered pulsars, rapidly pulsating radio sources that could be traced back to rotating, magnetized neutron stars, the ultra-dense, collapsed remains of massive stars.
This was one of the most exciting astronomical events of the second half of the 20th century: the precise timing of the pulses of these objects is more accurate than the best atomic clocks and enabled precision tests of general relativity.
The team Hewish assembled – Jocelyn Bell, John Pilkington, Paul Scott, and Robin Collins – all played a vital role in the detection and confirmation of the first pulsar, with attention naturally turning to Bell, the researcher who was the first to detect unusual signals .
Seven years later, Hewish and Martin Ryle were jointly awarded the Nobel Prize in Physics, “for their pioneering work in radio astrophysics: Ryle for his observations and inventions, particularly aperture synthesis technology, and Hewish for his decisive role in the discovery of pulsars”.
Ryles and Hewish’s invention of aperture synthesis in 1960, which uses the rotation of the earth to effectively convert a number of telescopes into a single giant circular antenna, was critical to the development of radio astronomy. The Very Large Array in New Mexico, the Atacama Large Millimeter / Submillimeter Array (Alma), the European Low-Frequency Array (Loray) and the Event Horizon Telescope for mapping black holes are modern examples of their innovation.
Hewish’s first research was on the propagation of radio waves through lumpy transparent media, and he realized in 1952 that the twinkle or twinkle of the recently discovered radio “stars” (actually radio galaxies or quasars) could be used to determine the conditions in the ionosphere and the interplanetary medium.
Today these techniques are used to depict large-scale structures in the solar wind. Hewish showed that interplanetary scintillations can be used to make very high resolution observations of distant objects, equivalent to a telescope with a baseline of 1,000 km.
He came up with the idea of a giant phased array antenna that could do a large survey of radio galaxies and quasars, and in 1965 secured the funds to build paper strip chart records from the array. It took them all to build the 1.8 acre array with its 1,024 dipole antennas.
After commissioning, Hewish asked Bell to make sky maps of the daily observations. True astronomical sources would return to the same location in the sky every day, while man-made disturbances would occur randomly. On August 6, 1967, Bell noticed an unusual spot on the maps that appeared from time to time in the same location in the sky.
Hewish decided to improve the time resolution of the recorder and this showed that the source pulsed every 1.33 seconds. Careful work by the team showed that the source was not due to an instrumental effect or “little green men”, but came from a source 200 light years away. Bell also discovered three other pulsars. Hewish, along with Bell and the three other authors, wrote the results down for publication in Nature.
His interpretation was that the source had to be either a rotating white dwarf star or a neutron star. The neutron star interpretation was soon confirmed by the discovery of a pulsar with a much shorter period in the Crab Nebula. In an interview, Hewish said that when Stephen Hawking heard the news, he called to say that if neutron stars existed, then black holes would almost certainly occur.
Born in Fowey, Cornwall, the youngest of three sons to Frances (née Pinch) and Ernest Hewish, a bank manager, Antony grew up in Newquay, where he developed a lifelong love of swimming and boating. The family lived above the bank, where his father was a manager, and Antony was allowed to set up a laboratory there. One of his early experiments with electricity blew the fuse in the entire building. At the boarding school – King’s College in Taunton – he built a crystal radio because normal radio was not allowed in the dormitory.
In 1942 Antony went to the University of Cambridge to study science. His studies were interrupted from 1943 to 1946 by war work on airborne radar defense equipment at the Royal Aircraft Establishment at Farnborough and the Telecommunications Research Establishment at Malvern, where he met Ryle.
He returned to Cambridge in 1946, graduated two years later, and immediately joined Ryle’s research group at the Cavendish Laboratory as a research student. After receiving his doctorate in 1952 on the fluctuations of galactic radio waves, Hewish became a research fellow at Gonville and Caius College and in 1961 moved to Churchill College as director of physics.
In 1961 he became a university lecturer, in 1969 lecturer and in 1971 professor of radio astronomy until he retired in 1989 when he was appointed professor emeritus at Cambridge. When Ryle fell ill in 1977, Hewish took over the leadership of the radio astronomy group in Cambridge and was from 1982 to 1988 director of the Mullard Radio Astronomy Observatory.
The award of the Nobel Prize to Hewish and Ryle was immediately controversial, criticizing, among others, Fred Hoyle and Thomas Gold for the exclusion of Bell, later Dame Jocelyn Bell Burnell.
Hewish was undoubtedly the main actor in the work that led to the discovery, inventing the scintillation technique in 1952, leading the team that built the array and making the discovery, and providing the interpretation as being due to a white dwarf or neutron star. Bell himself was friendly, saying, “I think it would demean a Nobel Prize to be awarded to research students, except in very exceptional cases, and I don’t think that’s one of them.”
After discovering pulsars, Hewish continued his work on interplanetary scintillations and the mapping of solar winds and “interplanetary weather,” which can have a dramatic impact on terrestrial communications.
In addition to his honorary membership in numerous foreign academies, he was made a Fellow of the Royal Society in 1968 and received the Eddington Medal of the Royal Astronomical Society in 1969 and the Hughes Medal of the Royal Society in 1977. A shy, humble man, Hewish turned down offers to become a Masters at a Cambridge college.
He believed that science and religion were complementary and that: “We should be ready to accept that the deepest aspects of our existence are beyond our understanding of common sense.”
Antony married Marjorie Richards in 1950 and they had a son, Nicholas, and a daughter, Jennifer, who died in 2004.
Marjorie and Nicholas survive, as do five grandchildren and three great-grandchildren.