Pulsars are powerful cosmic lighthouses. They are swiftly rotating magnetized neutron stars that emit high-energy electromagnetic radiation. They are a particularly useful tool for astronomers since they can be used to probe the space between galaxies and even act like precise clocks. Due to their regularity, they are used in maps of the cosmos, hence the relative position of the Sun to pulsars was etched on the Voyager golden record. Yet for me, the discovery of pulsars is the most fascinating. It is a story of passion, perserverance, and ingenuity that is very inspiring to future researchers.
Jocelyn Bell Burnell was born in 1943 in Northern Ireland. Her dad was an architect who designed the Armagh Planetarium. Through her visits there with her father and by reading books, she became interested in astrophysics as a child. Her education was difficult due to the social norms for women. She went to a prestigious grammar school, yet only boys were encouraged to study technical fields. Her parents had to convince the school to change its policy in order for Burnell to study science. She eventually graduated with a BS from the University of Glasgow and went on to pursue a Ph.D. at Cambridge, which she completed in 1969.
Her graduate work coincided with a boom in radio telescopes. Alongside Anthony Hewish, she worked on constructing the Interplanetary Scintillation Array. Scintillaton is random fluctuation in the intensity of the radio waves emmited by objects from space. It is mainly caused by changing refractive properties of the solar wind. Think of an analog with visible light. From high school physics we know that water refracts light because it is denser than air, so light travels more slowly through it. Now imagine a mixture of water and oil that we stir vigorously. If we shine a beam of light through it, some of the light will hit larger oil droplets and some will just pass through the water. The uneven diffraction will cause intereference between different beams and thus irregularities in the amplitude. The solar wind plasma is a mix of electrons and protons that varies in density, so it acts like the water and oil mixture but for radio waves.
The main goals of constructing this array were investigating scintillation in more depth and looking for quasars, which are massive, and luminous active galactic nuclei powered by huge black holes. Burnell spent her research reviewing massive printouts from the instruments, looking for interesting details. In November 1967, when analysing signals from that summer, she found an anomaly. It appeared that a signal repeated itself every 1.33 seconds with imense regularity. It couldn’t be a coincidence and random scintillations could not explain it. The source was jokingly dubbed LGM-1 for Little Green Man, as some publications pondered if the regularity could come from alien communications. Burnell described her discovery as a pulsating radio source, which was shortened to pulsar by a BBC correspondent.
Yet, despite her brilliant discovery the prejudice of society towards women still deeply affected her. In a 2020 Harvard lecture she disclosed, that when the research team was discussing their discovery Hewish would be asked about the physics, while Burnell would be asked about the color of her hair and how many boyfriends she had. Moreover, she did not receive the 1974 Nobel Prize, despite building the Interplanetary Scintillation Array for two years, pursuading Hewish that this regular phenomenon was not just interference, and meticulously going over 30 meters of paper per night. Of course, her male supervisor received the award and was invited to speak in conferences across the globe.
Despite the injustice she faced in the academic world, she has been undeterred. She taught at a lot of universities, even acting as the president of the Royal Astronomical Society, and currently is a professor at Oxford. In 2018, she was awarded $3 million and the Breakthough Prize in Fundamental Physics. She spent the money on funding Ph.D. studies for physics students from underpriviledged backgrounds. Burnell often speaks about supervisors getting more credit than the students that carry out the experiment. Many of the greaterst discoveries in physics were actually made by graduate students. For instance, the Rutherfold gold foil experiment that showed that a nucleus is a dense positive charge, was actually carried out by his grad students Geiger and Marsden. While Hewish laid out the basics of scintillations in the 50s, it was Burnell who actually applied them. For anyone who has done independent experimentation in physics, you know how challenging and unexpected some of the things we have to deal with are. I strongly hope that more and more professors will give credit to their graduate students in their papers and during conferences.
I would like to finish this post with a personal update. I have been accepted to JHU, my dream school :). I’m planning to major in physics and I am very excited to write about research or interesting things I learn in classes. I will have a lot of free time soon, so I’m definitely going to review more books and maybe even new articles I find on arXiv. Thanks to everyone for supporting me on my high school journey!
References
Brown, M. (2020, November 28). “It’ll upset a few fellows”: Royal Society adds Jocelyn Bell Burnell portrait. The Guardian. https://www.theguardian.com/science/2020/nov/28/itll-upset-a-few-fellows-royal-society-adds-jocelyn-bell-burnell-portrait
Cofield, C. (2016, April 22). What Are Pulsars? Space.Com. https://www.space.com/32661-pulsars.html
Drake, N. (2021, May 4). Meet the Woman Who Found the Most Useful Stars in the Universe. Science. https://www.nationalgeographic.com/science/article/news-jocelyn-bell-burnell-breakthrough-prize-pulsars-astronomy
HEWISH, A., SCOTT, P. F., & WILLS, D. (1964). Interplanetary Scintillation of Small Diameter Radio Sources. Nature, 203(4951), 1214–1217. https://doi.org/10.1038/2031214a0
Wikipedia contributors. (2022, February 11). Jocelyn Bell Burnell. Wikipedia. https://en.wikipedia.org/wiki/Jocelyn_Bell_Burnell