Louise Webster (1941-1990): a trailblazing astronomer who co-discovered the first black hole

Introduction

The theme of this years United Nations International Day of Women and Girls in Science (IDWGIS) is “Synergizing AI, Social Science, STEM and Finance: Building Inclusive Futures for Women and Girls.” Astronomy is a science at the forefront of technological innovation and there are Australian women astronomers whose work is and was technological in nature and ground breaking. However, apart from Ruby Payne-Scott whose mathematical and innovative work in radio astronomy has been acknowledged, (1) few others are well-known.

Caption: Photo of Louise Webster, Credit Storey and Faulkner (1991) (6)

Louise Webster is a ‘hidden’ outstanding Australian astronomer, whose co-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 (2) and British science journalist Marcus Chown (3). In October 2024 Chown was interviewed by Robyn Williams 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' (4)

In 2024 Hon Professor Nick Lomb and I were researching the Astronomical Society of Australia (ASA), which was formed in 1966. We examined the lists of members, examining gender diversity, the locations and types of astronomy-related organisations that employed ASA members and student member demographics (5). Our research revealed that 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. This blog post acknowledges Webster.

Louise Webster (1941–90)

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 (6). 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 (7). Her thesis was accepted in 1966 (8) 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 (6,9).

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 (9). 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.

Caption: The Isaac Newton telescope, Herstmonceux ~1970s. Courtesy The Observatory Science Centre.

Using the Isaac Newton telescope (pictures above) 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 (10). Webster focused 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 (11) that ‘…it is inevitable that we should also speculate that it might be a black hole.’ Webster was the lead author of the paper.

Image left caption: Illustration of Cygnus X-1 courtesy NASA/CXC/M.Weiss. Showing the black hole, identified by Webster, pulling material from the massive blue star.

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 (6). 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 (ASA) and her leadership led to the ASA annual scientific 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 (6).  

In 1989 Webster  was elected to the ASA Council, sadly she died the following year.at the early age of 49, and 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 (6). In 2009 the ASA named a prize in her honour and each year since this has been awarded to early career researchers (5).

On International Day of Women and Girls in Science (11 Feb) we remember and acknowledge Louise Webster as an extraordinary Australian scientist.

References:

1.     Goss, M.. (2013) Making Waves: The Story of Ruby Payne-Scott: Australian Pioneer Radio Astronomer 2013., Springer Nature, Berlin, Heidelberg; Goss, M (2009) Under the Radar: The First Woman in Radio Astronomy: Ruby Payne-Scott 1st edn R McGee (ed), Springer Nature, Berlin, Heidelberg.

2.     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.

3.     Chown, M. (2024) ‘The woman who discovered black holes’ blogpost, New Humanist. https://newhumanist.org.uk/articles/6296/the-woman-who-discovered-black-holes; Chown, M. (2023) Chown, M 2023, The one thing you need to know: the simple way to understand the most important ideas in science, Michael O’Mara Books Limited, London, p.p. 147-8.

4.     ‘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

5.     Stevenson T., Lomb N. (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 

6.     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 

7.     Betty Louise Webster thesis, ANU. http://hdl.handle.net/1885/138438

8.     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 

9.     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).

10.  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

11.  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

Note: A version of this blogpost, written for International Women's Day 2025, was published on Sydney City Skywatchers website.