Louise Webster (1941-1990): the first astronomer to identify a black hole.
This blog post is part of an annual series to recognise Australian women in astronomy on International Women’s Day, 8 March.
Introduction
In 2024 Professor Nick Lomb and I were researching the Astronomical Society of Australia (ASA), which was formed in 1966. We examined the lists of members, focussing on gender diversity, the locations and types of astronomy-related organisations that employed ASA members and student member demographics. From this research two papers were published in the Historical Records of Australian Science, a CSIRO journal. The first paper examined the types, nature and location of observing facilities within the context of ASA membership (1). The second paper tracked changes in gender diversity and highlighted strategies and the growth in both the percentage of women studying and employed in astronomy and the increased percentage of women who are fellows, indicating leadership in the field (2).
Our research revealed that women constituted 4% of the ASA membership in 1969. By 2023 this had increased to 31% and the percentage of women elected as ASA Honorary Fellows increased from zero in 2010 to 23% in 2023. Many of the early women professional astronomers and PhD students went on to have outstanding careers, but their research was sometimes hard to find due to surname changes after they married. The 1969 list of women who were ASA members included Anne Green (nee Barwick), Margaret Clarke, Joyce Ekers (nee Billings), Beverley Wills (nee Harris), Donna Dee Shinkawa (nee Hain), Pamela Kennedy, Jeanette Merkeli, Marilyn Mowat, Lindsey Fairfield Smith, Reet Vallak, and Louise Webster, who was also known as Betty Louise Turtle after she married Sydney University astronomer Anthony ‘Tony’ J Turtle. Recently Webster has been recognised as a ‘trailblazing’ astronomer making a big impact on astronomy globally.
Louise Webster (1941–90)
When Australian astronomer Louise Webster passed away at the early age of 49, astronomers mourned the loss of an outstanding scientist. An obituary outlined her discovery of a black hole, contribution to the advancement of astronomy, education and mentorship of others (3). In 2009 the ASA named a prize in her honour and each year since this has been awarded to early career researchers (2).
Louise Webster was born in Adelaide in 1941. She was the only woman in the physics class at Adelaide University where she studied for an undergraduate science degree (3). Webster excelled and obtained a scholarship to research southern planetary nebulae at the Australian National University (ANU) for her PhD. At Mt Stromlo Observatory, under Directorship of Bart Bok and supervised by Bengt Westerlund, Webster observed and analysed the characteristics (distance, relative position brightness and temperatures) of nebulae in the Magellanic Clouds (3). Her thesis was accepted in 1966 (4) and is now available online. She presented at an International Astronomical Union symposium in 1967, and then worked as an instructor at the University of Wisconsin and published research papers related to planetary nebulae (3,5).
In 1969 Webster was employed as a Scientific Officer by the Royal Greenwich Observatory at Herstmonceux in Southern England. Here she observed using the 98 inch (almost 2.5 metres) Isaac Newton reflector telescope (INT). The observer can sit inside this telescope (as shown in the image below) and when it was inaugurated in 1967, it was the largest telescope outside the USA and Russia (6). It was similar to the smaller 74-inch (1.9-m) telescope at Mt Stromlo, which Webster would have been familiar with. Within a year she was promoted to Senior Scientific Officer.
Using this telescope Webster measured the spectra of stars to determine their speed. Next to her desk sat fellow astronomer Paul Murdin, who was examining the results of NASA’s recently launched X-Ray telescope satellite. To solve a mystery as to the origin of an X-Ray source in the constellation Cygnus, they combined their knowledge and began to theorise as to what could be causing the X-ray source, called Cygnus X-1 (7). Webster focussed her observations on a super-massive blue star adjacent the Cygnus X-1 source to look for a companion star which could solve this puzzle.
Finding no companion star, Webster and Murdin concluded in their paper published in Nature in 1972 (8) that ‘…it is inevitable that we should also speculate that it might be a black hole.’
In 1974 Webster was promoted to Principal Scientific Officer, she worked on a South African branch of the observatory and then as commissioning officer of the Anglo-Australian telescope, where she became staff astronomer (3). In 1979 Webster accepted a position at the University of New South Wales (UNSW) where she contributed significantly to the development of the astrophysics curriculum and capability.
Webster was active in the Astronomical Society of Australia and her leadership led to the annual conference being held at UNSW in 1983. She was appointed Head of the Department of Astrophysics and Optics at UNSW and was project lead on the development of a new telescope at Siding Spring Observatory (3).
In 1989 Webster was elected to the ASA Council, sadly she died the following year.
Louise Webster’s identification of the first fully plausible black hole remained largely unknown to all outside professional astronomy, perhaps due to her modesty. In recent years she has been recognised by astrophysicist Alistair Graham et al (9) and British science journalist Marcus Chown (10). In October 2024 Chown appeared on the ABC’s Radio National The Science Show and said:
‘Incredibly Louise Webster, an Australian woman, was the co-discoverer of black holes, and she has been largely written out of history and forgotten” (11)
It’s time to remember her!
References:
1. Lomb Nick, Stevenson Toner (2024) Spreading across the continent: the Astronomical Society of Australia 1966–2023. Historical Records of Australian Science 36, HR24020, https://doi.org/10.1071/HR24020
2. Stevenson Toner, Lomb Nick (2024) Gender diversity in Australian astronomy: the Astronomical Society of Australia 1966–2023. Historical Records of Australian Science 36, HR24022, https://doi.org/10.1071/HR24022
3. Storey, J.W.V. and Faulker, D.J. (1991) ‘Betty Louise Turtle, 1941–1990’, Publications of the Astronomical Society of Australia, 9(1), pp. 6–7. https://asa.astronomy.org.au/wp-content/uploads/2020/09/Webster.pdf
4. Betty Louise Webster thesis, ANU. http://hdl.handle.net/1885/138438
5. Webster, Louise (1969) The masses and galactic distribution of southern planetary nebulae. Monthly Notices of the Royal Astronomical Society 143, 79. https://doi.org/10.1093/mnras/143.1.79
6. Corben, P., Hobden, D., Jones, D., Nicholson, B., Scales, B., Selmes, R., Wallis, R., Wilkins, G. (2006) Astronomers at Herstmonceux: in their own words, Science Projects Publishing, East Sussex, Wilson, A (ed).
7. Murdin, P. (2023). ‘Webster, B. Louise’, in: Nicholson, P.D., Bartlett, J.L. (eds) Biographical Encyclopedia of Astronomers. Springer, New York, NY. https://doi.org/10.1007/978-1-0716-0738-1_101023-1
8. Webster, B.L., Murdin, P., (1972) Cygnus X-1-a Spectroscopic Binary with a Heavy Companion ?, Nature 235, 37–38. https://doi.org/10.1038/235037a0
9. Graham, A. W., Kenyon, K. H., Bull, L. J., Lokuge Don, V. C., & Kuhlmann, K. (2021). History of Astronomy in Australia: Big-Impact Astronomy from World War II until the Lunar Landing (1945–1969). Galaxies, 9(2), 24. https://doi.org/10.3390/galaxies9020024
10. Chown, M (2024) ‘The woman who discovered black holes’ blogpost, New Humanist. https://newhumanist.org.uk/articles/6296/the-woman-who-discovered-black-holes
11. ‘A Crack in Everything’, ABC Radio, The Science Show, Marcus Chown interviewed by Robyn Williams, 5 October 2024. https://www.abc.net.au/listen/programs/scienceshow/marcus-chown-a-crack-in-everything/104436398
Related International Womens Day blogpost:
Links will shortly be provided for the following blogposts:
Mary Acworth Evershed (nee Orr) – astronomer, author, eclipse chaser
Miriam Chisholm: photographer, historian and eclipse chaser
Margie Ann Arnold: women who supported male astronomers
Prudence Valentine Williams: astronomer, leader, fair workplace champion
Muriel Agnes Heagney: Equal pay for women champion was one of the ‘hidden figures’ of Australian astronomy
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