Of Pulsars and Nobel Prizes


Photo credit: Louise Flanagan

IN 1967, a young woman was poring over data from an enormous radio telescope, when she noticed a peculiarity within the data and convinced her supervisor that it was worth further investigation. Her name was Jocelyn Bell (now Dame Jocelyn Bell Burnell) and she was seeing the very first evidence of pulsars. Bell and her PhD supervisor Dr. Anthony Hewish, published their findings and pioneered the field of pulsar research.

Hewish and Sir Martin Ryle went on to win the Nobel Prize for Physics in 1974; Bell Burnell did not. Ryle won for his work in the development of radio telescopes, Hewish for his role in discovering pulsars.

That Bell Burnell was not a recipient of the Nobel Prize despite being the first to observe and analyse the data for pulsars has been widely criticised, but it never stood in the way of Bell Burnell’s enthusiasm for physics. She continued to work in astronomy, made many contributions to the field, and has received a great number of accolades and awards (including a damehood in 2007).

Last week she visited UCD, her first visit here, to speak at an event hosted by UCD Physics Society, where she gave an address to roughly 100 people, a mixture of students and staff, all about pulsars, a field of study made possible by her.

Bell Burnell first realised physics was her passion in school at the age of 12. She recalls “as soon as we started physics in school… it was clear I was good at it”. And other science subjects did not appeal to her “doing chemistry was okay, doing biology I found boring, so physics it was. And then about mid-way through my teens I discovered astronomy and astrophysics and decided if I could that would be the bit of physics I went into ultimately.”

And so it was, she studied physics (then called natural philosophy) at University of Glasgow, after which she joined a research group at Cambridge studying quasars. The group was capturing radio waves using a radio telescope. Radio telescopes capture radiation emitted from objects in outer space at radio-frequencies as an antenna.

Bell Burnell “and about half a dozen of us, together” built a radio telescope which “covered an area of 57 tennis courts” (roughly 4 and a half acres). The size of the radio telescope aided it to collect sufficient radio waves for analysis, as the radio waves are weakened as they travel across vast distances through space. According to Bell Burnell, “It’s perhaps not what people think of as a radio telescope today, it was a lot of wire, wooden posts, cables, it was big. It. It looked more like an agricultural frame than a piece of scientific equipment.”

Bell Burnell’s role in the group was to analyse the data produced from the telescope. The data would be printed on large sheets of paper and she would have to physically look through it. While doing so, she noticed funny smudges in the data and, looking closer at it, realised that they were pulses spaced 1.3 seconds apart, always found at the same place in the night sky at a certain time every night. Unsure what they were she looked elsewhere and found more. She co-authored a paper with her supervisor detailing the discovery of these pulsating anomalies which became dubbed “pulsars”, small dense objects which spin and release radiation at their poles, which sometimes are directed at the Earth.

Assistant Professor of Astronomy in UCD Dr. Antonio Martin Carrillo, describes pulsars as “when a massive star explodes, and dies, the remnant is a neutron star, a very small and dense neutron-rich star. The density gives rise to ‘a huge gravitational field and a really strong electromagnetic field’. At the magnetic poles, a beam of electromagnetic radiation is given off which is detectable by radio telescopes. The beam gives a ‘lighthouse effect, its beam is towards you and see it bright and then it goes off and then on, and off and on. But at a millisecond scale, so really, really fast”.

The discovery of pulsars has provided scientists with methods of studying other space phenomena, such as gravitational waves. Einstein’s theory of general relativity predicts the existence of gravitational waves. They are ripples in space-time caused by extremely violent events such as the fusion of supermassive black holes. Pulsar timing arrays are being studied to prove their existence. A group of pulsars with radio pulses spaced milliseconds apart are used. When an event causes gravitational waves to propagate, tiny differences in the timing of the pulses from different pulsars can be detected allowing the source and strength of the waves to be analysed.

In her talk, Bell Burnell’s passion, enthusiasm and love for her subject matter is clear. She delivers her talk effortlessly (she is after all one of the pioneers of pulsar research), casually dropping jokes about “little green men” and she uses her hands for regular demonstrations. Not alone her knowledge of the subject, but her delivery, make it clear that she is an excellent teacher, and that the past controversy (not receiving the Nobel Prize) has not dampened her love for physics.

When I ask about her feelings surrounding the controversy she reveals she regrets “wearing her engagement ring to work”. Bell Burnell describes the pulsar discovery as “all such huge fun, and also very worrying, it’s a lot of strong emotions all at the same time”, but believes her intentions to get married (which she did) prevented others in her field from taking her seriously, believing she would give up work after marriage. “Married women weren’t expected to work, in fact it was shameful if a married woman had to work. I didn’t want to give up work, but because you’re wearing an engagement ring the assumption is that you’re giving up work.”

For a woman with a damehood for her services to sciences, she puts on no airs and graces. Before and after her talk she happily spoke to any student who approached her and she encourages anyone who wants to do physics to “go for it”. She speaks of “a huge need for physicists” and says there’s “a huge range of opportunities open to you, so go for it”.

Bell Burnell continued to work diligently in astrophysics, she persevered and excelled in her research field, despite being overlooked for the Nobel Prize. She refused to let the controversy of the decision ruin her love of physics. She demonstrates what is truly important when working in a subject field in which you are passionate, the work, and subject matter itself, and not the awards. Dame Bell Burnell’s dedication to astrophysics, stemming from a time when it was not typical for women, has, and will be, an inspiration for future generations of physicists.

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