Nigeria’s First Radio Astronomer

Prof Samuel Okoye

Samuel Ejikeme Okoye (1939–2009) was the first Black African astronomer to achieve a PhD in radio astronomy. He did so at the University of Cambridge in 1965, at the time when radio astronomy was beginning to reveal the high-energy universe. He went on to play a major part in establishing astronomy in Nigeria as both a discipline in itself and to drive development.

Writing in 1990, Okoye described himself as “a fresh physics graduate who was persuaded … to do a doctorate degree in radio astronomy at the University of Cambridge, UK … It was this same resource person, who some years later had seen to the injection of a good quantity of astronomy topics into the national science curricula at both the primary and secondary levels; the initiation of astronomy programmes at the University of Nigeria, Nsukka … the transformation of the former department of physics into the present department of physics and astronomy; and the recent establishment of a Space Research Centre at the University of Nigeria.” The influence of this “resource person” has persisted. Nigeria now hosts a regional branch of the International Astronomical Union Office of Astronomy for Development (IAU OAD), and radio astronomy is proving a powerful agent for technological growth across Africa as a whole – something highlighted by the choice of Cape Town, South Africa, to host the 2024 IAU General Assembly.

Out of Africa

Okoye was born in Amawbia in Anambra state, Nigeria, on 26 July 1939. He did well at the local school and won a scholarship to board at the Government Secondary School in Owerri, more than 100 km away. Physics was not then considered an especially useful subject to study and university places went only to students who were both clever and determined. Okoye won a place at University College Ibadan, established in 1948 as a college of the University of London. It was the first university in Nigeria and became independent, awarding its own degrees as Ibadan University, in 1963. Okoye graduated in 1962 with first-class honours in Physics and the departmental prize. He continued his education with a PhD at the University of Cambridge, UK, with funding from a Carnegie Foundation Fellowship, a competitive award open to students from all over the world.

Okoye arrived at Churchill College Cambridge in 1962, an exciting time in astrophysics (see box “Post-war radio astronomy at Cambridge”). The research group he joined had by then expanded to become the Mullard Radio Astronomy Observatory. Okoye was supervised by Antony Hewish and investigated the structure of the interplanetary medium using scintillation. This was an observational project and research students at the time were expected to be quite literally hands-on, helping to build the instruments that they used (Bell Burnell 2003). Okoye played his part in constructing two corner reflector antennas and their beam-switching circuits for a 38 MHz instrument and building 13 preamplifiers for the 13 km cable link (described in Hewish & Okoye 1964). This instrument allowed Okoye to investigate the radio source in the Crab Nebula, catalogued as 3C144, finding unusual intensity variations in part of the signal. Scintillation analysis showed that the source of this component had an angular diameter of about 0.1 arcsec (Hewish & Okoye 1965). Assuming it was coincident with the visible Crab supernova remnant, the source was about 1 milliparsec (200 au), with a brightness temperature of 1014K (Hewish & Okoye 1964). These results raised a lot of questions about the nature of this unusual source: it was far too small to be explained by conventional synchrotron radiation. Hewish and Okoye (1964) suggested that they may have found signs of “an active remnant of the supernova explosion”.

Sam Okoye at the 17th IAU General Assembly in Montreal, Cananda, in 1979. (AIP Emilio Segrè Visual Archives, John Irwin Slide Collection)

We now know that the radio signal from the Crab nebula comes from a fast-spinning neutron star around 20 km across: a pulsar (figure 2). But this was the first indication that radio signals could come from such small sources. In 1967, after using her own set of pliers to help build a larger telescope covering 4.5 acres (one 50th of a square kilometre), Hewish’s research student Jocelyn Bell Burnell spotted a signal with a period of 1.3 s (Bell Burnell 2003). Hewish received the 1974 Nobel Prize in Physics for the discovery, sharing the award with Martin Ryle, who was recognized for his wider contribution to radio astronomy. In his acceptance speech, Hewish mentioned the research he had carried out with Okoye as a significant step towards the discovery of pulsars.

The Crab nebula with the Crab pulsar (right-hand of the pair of bright stars near the centre). (NASA and ESA; J Hester [ASU] and M Weisskopf [NASA/MSFC])
The Crab nebula with the Crab pulsar (right-hand of the pair of bright stars near the centre). (NASA and ESA; J Hester [ASU] and M Weisskopf [NASA/MSFC])

Home again

Okoye returned to Nigeria after his PhD as a lecturer at the University of Ibadan. He became a Fellow of the Royal Astronomical Society in 1966, the same year that he moved to the University of Nigeria, Nsukka (UNN), where he spent the rest of his career. Nsukka is in eastern Nigeria, the region where Okoye had grown up. UNN was the first fully-fledged and autonomous university in the country, opened in 1960 as part of the celebrations of Nigerian independence. Okoye set about building his career in astrophysics.

It didn’t go well. Nigeria had been a British colony since 1900, but increasing pressure for independence after the second world war ended its colonial era in 1960. The country became a republic in 1963, then a military take-over in 1966 was the prelude to the three-year Nigerian Civil War and the formation of the short-lived Republic of Biafra in eastern Nigeria in 1967. An estimated 3.5 million people died before the war ended in 1970.

Post-war radio astronomy at Cambridge

Radio astronomy benefited from the experience of researchers such as Martin Ryle, Bernard Lovell and Antony Hewish who worked on radar during the second world war. Military interest in radio signals from the Sun and stars was limited to minimizing their interference in radar location, but wartime technology was later used to advance this new field.

At that time a few discrete radio sources had been discovered, including a source in the constellation Cygnus known as Cygnus A, in 1939. But determining their size – and location – was a problem. In 1946, Martin Ryle and colleague Derek Vonberg at Cambridge University’s Cavendish Laboratory adapted war surplus equipment to create a novel instrument: a radio interferometer. With this instrument, its antennas separated by a few hundred metres, they could locate sources in the sky, to some extent, and put limits on their size and brightness. Ryle’s team went on to modify the interferometer, adding the phase-shift receiver that separated signals from compact sources from the galactic background (Ryle 1952). They surveyed the sky, starting the series of Cambridge catalogues (1C, 2C etc) of radio sources.

Antony Hewish completed the undergraduate degree interrupted by his war service and joined Ryle’s radio astronomy research group in 1948. He first worked on the effects of the ionosphere on radio signals from more distant sources, using distortion of the incoming radio emission to map ionospheric plasma (Hewish 19511952). Irregularities in the refractive index of ionospheric plasma affect radio signals in much the same way variations in the refractive index of the atmosphere distort visible light. Stars twinkle; radio sources scintillate. Hewish established that when signals from what were then called radio stars passed through the solar corona they also scintillated (Hewish 1955).

In her PhD research, Margaret Clarke noted that three radio sources in the 3C survey fluctuated in intensity as if undergoing severe ionospheric scintillation (Clarke 1964). Hewish et al. (1964) followed up this observation, finding that 3C119, 3C138 and 3C147 showed random intensity variations on a timescale of 1–2 s. They deduced that irregular ionospheric plasma could not reproduce this pattern, but interplanetary plasma could. Any sources affected by such scintillation would have to be small; just as in the visual range, where stars twinkle while planets, with bigger angular diameters, do not. Clarke (1964) had pointed out that two sources (3C119 and 3C147) also had unusually small angular diameters. Hewish et al. (1964) determined that 3C48, 3C119 and 3C138 must have angular diameters less than around 0.3 arcsec.

In 1969, Okoye married Chinyere Ucheime Obioha, a librarian at UNN; they went on to have four children. During this time he continued his research, publishing, for example, on variations in plasma density (Okoye & Hewish 1967). He also made plans to establish a radio astronomy observatory in Nigeria. But by 1971 it became clear that no funding would be forthcoming for such an enterprise; as a result Okoye started to develop his interests in theoretical astrophysics. His boss, Prof. J O C Ezeilo, the vice-chancellor of the UNN, approved; in the words of cash-strapped administrators everywhere, he wrote that this was a subject that could “be pursued in this university at little or no cost to the university” (Churchill College Archives). Okoye knew that he needed to travel to get up to speed; he looked for posts in the USA, but also applied for a Commonwealth Academic Staff Fellowship “to acquire some advanced mathematical techniques and seek out relevant theoretical solutions to current problems in astrophysics”, as Ezeilo put it.

Okoye contacted his former colleagues at Cambridge. Both Hewish and Ryle recommended him strongly for the position. “Okoye is clearly a competent man, with drive and initiative, who can tackle both experimental and theoretical aspects of a project,” wrote Hewish in 1971. “On returning to Nigeria he was just planning his own research when the civil war commenced and terminated his activities. When we re-established communications many months later it was clear that observational work in radio astronomy was out of the question and Okoye them turned his attention to theoretical studies.” Ryle also wrote very positively in support of Okoye: “Not surprisingly, following the last difficult years he is feeling particularly cut off scientifically from the world and wants very much to make contact again with work which he might be able to continue at Nsukka.”

Back to Cambridge

Okoye returned to Cambridge in 1971–72 as a Commonwealth Academic Staff Fellow at the University of Cambridge, visiting fellow at the Institute of Astronomy (IoA), Cambridge and a fellow commoner of Churchill College. He worked at the IoA, supervised by Fred Hoyle, catching up on plasma physics, general relativity and cosmology and establishing his own high-energy astrophysics research, publishing on X-ray data from radio galaxies and the jet of M87 (Okoye 19721973). He also secured donations of laboratory teaching equipment from the Department of Physics at Cambridge for the UNN, and school equipment from an educational charity for a school in the region, to help recover from the civil war. He enjoyed his time at Churchill College and particularly appreciated the kindness of the college in paying for his wife and young children to come to Cambridge with him.

Back in Nsukka, Okoye steadily gained promotion. While at Cambridge he had developed contacts in the UK and more widely and was also able to visit Leiden Observatory in the Netherlands and the National Radio Astronomy Observatory in Charlottesville, Virginia, USA. He steadily increased the capacity for astronomy in his department and in 1972, set up the Space Research Centre at UNN as a focus for astronomy and space activity in Nigeria. He became a professor in 1976 and by the late 1970s he was taking on more general university responsibilities such as the head of the department at the same time as the numbers of students studying astronomy grew; he ended his career at UNN as dean of the School of Postgraduate Studies. In 1982, Okoye became a fellow of the Nigerian Academy of Science.

Okoye continued to improve the position of astronomy in Nigeria at the same time as exploring the subject as a means of development. He focused on reforming science teaching and education in his home state, Anambra, but also represented his country internationally, at the UN Conference on the Peaceful Uses of Outer Space in Vienna in 1982, for example, in the IAU (which Nigeria joined in 1985). He wrote extensively on ways to use science and technology in developing countries, including reports on technology transfer (Okoye 1977). In 1987, he published a book on basic science development in Nigeria (Okoye & Onuoha 1987) He was also a champion of African culture, for example, suggesting ways to use indigenous languages for science (Okoye 1978).

Throughout this time he was also working to establish astronomy – and radio astronomy – in Nigeria. Okoye continued to pursue high-energy astrophysics research, writing in favour of the Giant Equatorial Radio Telescope (Swarup et al. 1979) and advocating a Nigerian Space Programme (Okoye 1981). In 1984, he organized the donation of a 10 m radio dish from the Hat Creek Observatory in California, USA (figure 3). Okoye intended this to become part of a Very Long Baseline Interferometry station to work with the European and worldwide networks then being established. Although the dish was installed and had the potential to support pulsar work (Okoke 2011), the lack of infrastructure and financial support meant that it ceased operations in 1987 (Okeke 1999).

Okoye (fourth from left, back row) and team with the 10 m dish at the Nnamdi Azikiwe Space Research Centre. (NASRD)
Okoye (fourth from left, back row) and team with the 10 m dish at the Nnamdi Azikiwe Space Research Centre. (NASRD)

On the international stage, Okoye attended 12 Pugwash Conferences on Science and World Affairs in the years 1979–91, serving as a member of Pugwash Council from 1988–93. These meetings, started in 1957, promoted dialogue between nations to free the world from the dangers of nuclear and other weapons of mass destruction. In later years they sought also to develop and support the use of scientific, evidence-based policymaking. Okoye’s contributions were in the area of science for development (Okoye 1980Smith & Okoye 1994).

Ill health led to Okoye passing on some of his responsibilities at UNN in 1986, and he moved to London in 1989. In 1991, he was once again in Cambridge, as a fellow commoner at Churchill College. Hewish had again recommended him for this position, which allowed Okoye to take up visiting research scientist positions at the Institute of Astronomy and the Radio Astronomy Research Group of the Cavendish Laboratory. He continued to supervise research students at UNN and went back to his research roots, exploring extragalactic objects through gravitational lensing and the effects of galaxy mergers (Okoye & Onuora 1996). This stay in the UK was a consequence of his ill health, but support he received from the Scientific Relief Fund administered by the Royal Society transformed “his enforced and unexpected sojourn in this country into a true academic sabbatical”, as Hewish put it.

Okoye was appointed science attaché to the High Commission of Nigeria in London in 1993 and held that position until 2000. He continued to advocate for science and technology for developing nations in general, and for Nigeria in particular. He became a British citizen in 2005 and died in London on 18 November 2009.


When Okoye started his career, politicians and officials in his native Nigeria believed that astronomy was an esoteric topic of little practical use (Okoye 1990). His sustained efforts to bring astronomy to Nigeria throughout his career were repeatedly frustrated by lack of funding and practical support. Yet he maintained his interest in high-energy astrophysics, keeping in touch with Hewish and other supporters at the University of Cambridge and developing new research contacts in the USA and Europe, as well as across Africa. His efforts resulted in the UNN teaching astronomy and space as part of its undergraduate physics course; masters and doctoral students followed. Nigeria developed a small space programme, launching its first satellite in 1996. The country has not yet established a significant radio telescope, although this remains an objective. The Space Research Centre at UNN was the forerunner of today’s Centre for Basic Space Research (CBSS) which opened in 2001, part of the National Space and Development Agency set up by the Nigerian government in 1999. The CBSS has research links with Nigerian universities and research institutes in Japan, South Africa, USA and Europe. The centre promotes research, teaching and outreach, including in climate and solar research and instrumentation as well as astronomy and – it is hoped – radio astronomy.

Sam Okoye may have been the first Nigerian radio astronomer, but he was certainly not the last. His vision for astronomy as an end in itself and as a tool for development – in Nigeria and elsewhere – is finally being realized. Radio astronomy is taking root across the continent, not least in South Africa, home to the Square Kilometre Array mid-frequency array. The UK-led Development in Africa through Radio Astronomy (DARA; is aiming to produce a technologically savvy workforce through radio astronomy. And now Nsukka is the home of the West African regional centre of the OAD, setting the seal on this remarkable turnaround in attitudes to astronomy.

Author’s Bio:
Dr Sue Bowler is editor of A&G and enjoyed discovering Sam Okoye from his publications and letters. If you know more about Sam Okoye’s life and work, please get in sb*****@ra*.uk">touch.

This work was first published on A&G, Oxford Academic Series.