In this series of posts, we sit down with a few of the keynote speakers of the 240th AAS meeting to learn more about them and their research. You can see a full schedule of their talks here, and read our other interviews here!
Becoming proficient with a sledgehammer is not typically part of doing a PhD in astronomy. Then again, neither is discovering an entirely new class of astronomical objects. In 1967, a graduate student at Cambridge University named Jocelyn Bell did both. Her story is one of both unexpected discovery and her struggles against the all-too-expected sexism she faced in the astronomy community.
The physics-minded daughter of an architect who helped design the Armagh Planetarium, Bell was exposed to astronomy at a young age through books like Fred Hoyle’s Frontiers of Astronomy, which she read cover to cover. Bell says that when she made the mental connection between the rotation of galaxies and her lessons on circular motion in school, “I suddenly thought, yeah, I like physics, I can be an astronomer.” She liked physics enough to obtain her undergraduate degree in physics from the University of Glasgow. The university caught her attention because of its astronomy classes, but when she found that they focused largely on positional astronomy, Bell changed her focus to astrophysics.
In the 1960s, like previous decades, women attempting to study astronomy faced hostility and exclusion. For instance, ten years earlier, Margaret Burbidge – a coauthor, along with Fred Hoyle and two others, of a groundbreaking paper on stellar nucleosynthesis – had been rejected from multiple positions because of her gender. Bell did not expect to be treated any better. There were only two options for graduate school in astronomy in Britain at the time, Cambridge University and Jodrell Bank Observatory at the University of Manchester. Bell had spent a summer at Jodrell Bank, but “the grad students there had said, you know, they won’t take a woman [as a PhD student],” Bell remembers. Thinking she would be rejected by Cambridge, she applied to Jodrell Bank nonetheless but never heard back – a snub which she interpreted as “their way of not taking a woman.” While considering options for study in Australia, Bell decided to apply to Cambridge anyway – and was accepted.
At Cambridge, graduate students were expected to join a research group quickly. Bell’s research experience at Jodrell Bank gave her a head start over the others. Interested in quasars, she joined the group led by Antony Hewish. Quasars were a hot topic of research in the 1950s and ’60s. Today we know them to be supermassive black holes with accretion disks and energetic relativistic jets. When they were first discovered, however, they appeared more star-like; the term “quasar” comes from the descriptor “quasi-stellar radio source”. More and more quasars were being detected, but much about them remained mysterious. Astronomers hoped that more discoveries could lead to answers. The Cambridge quasar group planned to search for quasars by looking for scintillation, “twinkling” from radio waves passing through the solar wind. First, though, they needed to build a telescope.
At first glance, the Interplanetary Scintillation Array may appear to be a jumble of wooden posts and wires. Unlike the dishes of most radio telescope, it’s an array antenna, consisting of thousands of thin dipole antennas spread over several acres of fields. Constructive interference enhances the radio signal, which allowed the Cambridge quasar group to look for scintillating sources.
Building the IPS Array was a difficult task – both technically and physically. Bell was in charge of the electrical wiring, installing spark plugs and transistors. Most of the 1000 or so posts were left to the men in the group to hammer, but Bell “did enough that I could swing a sledgehammer – not one of the normal qualifications of a PhD.” She laughs. “I was playing field hockey at the time, and I could hit the ball from one end of the pitch to the other, which my teammates did not appreciate.”
The IPS Array was completed in two years, and Bell became the first and primary operator. She spent three weeks debugging and six months performing observations. “The telescope was a transit instrument with all the wooden poles,” she explains. “You couldn’t steer it in right ascension, but you could steer it in declination, and observe different strip declination strips of the sky.” The IPS Array’s data was written out by a chart recorder onto pieces of paper, plotting the intensity of the signal recorded by the telescope. “I think I ended up with five kilometers of that chart paper, if I remember, after six months observing,” Bell remembers.
Bell became skilled at distinguishing between signals from quasars and radio interference. Occasionally, however, she noticed a burst she couldn’t classify as either, marking it with a question mark. After seeing the same “piece of scruff” again and again, she pored through the shoe boxes containing data from earlier in her observing run. Bell and Hewish noticed that the source appeared in the same position in the sky. At her advisor’s suggestion, she increased the time resolution of the chart recorder – and saw that the scruff was actually a sequence of regularly spaced pulses. This raised eyebrows: could it be a satellite in a strange orbit? Had Bell made a mistake with the wiring?
Two things convinced the team that the scruff was a real astronomical source. First, another radio telescope at Cambridge also picked up the signal. Second, Bell found three other bits of scruff that looked similar, at different positions in the sky. These sources were dubbed “pulsars” due to the train of pulses that appeared at high time resolution. We now know that pulsars are the remains of some of the most massive stars, some spinning hundreds of times per second. Their powerful magnetic fields create beams of radio waves that sweep across the cosmos like lighthouses, creating the illusion of short pulses as the pulsar rotates.
While Bell found the first four pulsars and paved the way for the discovery of over 3,000 more, she did not stay in pulsar astronomy – nor did she initially receive the credit she deserved. Bell’s results were eventually published, but when the media covered her work, she was depicted as the “human interest” part of the story, while Hewish received most of the credit and eventually, unbelievably, a Novel Prize. Even her PhD thesis was ultimately on the quasars she had begun to study from her first weeks at Cambridge. Bell recalls, “My supervisor said it was too late to change the title of the thesis. . . From what I now know of university systems, I’m pretty certain he was wrong. . . But I was determined that the pulsars would go in somewhere, so they went in an appendix to the thesis.”
Not long after graduating, the newly-minted Dr. Bell married – becoming Dr. Jocelyn Bell Burnell – and had a child. The family moved every five or six years because of her husband’s job. “Both of those things enormously compromised my career,” she says. Forced to continuously find new positions, “I went from radio astronomy to gamma ray astronomy to X-ray astronomy to infrared and millimeter wave astronomy.” It would be about 20 years before Dr. Bell Burnell could pick a job she described as “my first choice, rather than fitting with somebody else’s. I became head of the physics department to fairly new university called the Open University and set up a group studying energetic binary stars at whatever wavelength was most useful. That group remains and has done very well.”
Prof. Bell Burnell’s work on pulsars led to the creation of an entire subfield of astronomy, and she continues to follow cutting-edge pulsar research, but her talk at AAS 240 will be on another subject which has been intertwined with her career: the prospects for women in astronomy. She mentions that data on the demographics of members of the International Astronomical Union shows that there has been a steady increase in the gender balance of the field. There are plenty of ongoing concerted efforts to address systemic inequity, including some led by Prof. Bell Burnell herself. In 2018, she was awarded the Special Breakthrough Prize in Fundamental Physics and chose to donate the more than $2 million she received to establish the Bell Burnell Graduate Scholarship Fund, administered by the Institute of Physics. It’s “for people from underrepresented groups. So in physics that in Britain that tends to mean women, people of color, people with disabilities, etc. The program’s now in its second year.” Prof. Bell Burnell mentions that she actually met with a group of recipients of the scholarship earlier today. “They’re in all branches of physics, but there are two or three in astrophysics.”
Still, Prof. Bell Burnell emphasizes a point that is clear to this day: in astronomy, like other fields, “the USA doesn’t do too well on gender, and Britain does even worse.” Astronomy may be far past the era when even prominent scientists like her and Burbidge were treated as second-class citizens simply because they were women, but there is a long, hard road to anything like true gender equality. In the meantime, I ask Prof. Burnell Bell for her advice – both about what she would have told herself back in the 1960s, and what she would tell graduate students today. She smiles. “Hang in there. You will survive.”
To hear more about women in astronomy, tune into Prof. Bell Burnell’s Plenary Lecture at 11:40 AM PT on Monday, June 13 at #AAS240!
Astrobite edited by: Pratik Gandhi
Featured image credit: American Astronomical Society