An Interview with Manuel F. Varela and Ann F. Varela: Who was Jocelyn Bell Burnell, and what did she have to do with Pulsars?

Jun 2, 2021 by

“Here I am trying to get a Ph.D. out of a new technique, and some silly lot of little green men have to choose my frequency and my aerial to try signaling us.”

—Jocelyn Susan Bell Burnell

Michael F. Shaughnessy

1) In this interview—we delve into astronomy and another famous female scientist—Jocelyn Bell Burnell. Where was Bell born, and where did she attend school in her youth?

Bell’s full name was Susan Jocelyn Bell. Her birthdate was July 15, 1943, in the town of Belfast, Northern Ireland. Her parents were well-educated Quakers who supported their daughter’s early interest in science with books and trips to the nearby Armagh Observatory, of which her architect father helped design. The staff at the observatory would also encourage her interest in astronomy during her visitations.

Bell attended the Preparatory Department of Lurgan College, a coeducational selective grammar school for students aged 14-19. Female students were not permitted to register for science classes at this institution until Bell’s parents, along with other parents, protested the school’s policy. Up to this point, the girl’s curriculum included cooking and needlepoint, but not any science-related courses. Despite her enthusiasm for learning, however, Bell struggled in grade school and failed an exam meant to measure her preparedness for higher education.

Undiscouraged, her parents sent her to England to study at a Quaker boarding school, The Mount School, where she promptly gained recognition for herself in her science classes. Having established her ability and talent for higher learning, Bell attended the University of Glasgow, where, in 1965, she earned her B. Sc. degree in physics with honors. She later earned a Ph.D. in radio astronomy from Cambridge University in 1969.

2) Her supervisor at Cambridge—Antony Hewish and radio galaxies—seemed to pique her interest. What was Hewish doing, and how did Bell fit into the picture?

In 1965, Bell started graduate studies in astronomy at Cambridge, working under her graduate advisor Anthony Hewish. At the time, Hewish was a radio astronomer designing and building a radio telescope to detect quasars in outer space. Quasars are incredibly bright centers of galaxies with supermassive black holes. See Figure 1.

These galactic centers are highly active from an electromagnetic perspective. Such highly active galactic centers of quasars are star-like objects with a circular accretion disk of hot gas. As the gas in the spinning disk is drawn into the supermassive engine of the black hole, the center becomes a compact source of radio wave emissions characterized by electromagnetic radiation with a wide-ranging spectrum. The matter that plunges into the depths of a black hole is heated by intense gravity, generating massive blasts of radiation beams. The edges of the spinning hot disks form a donut-shaped ring of stellar dust. So-called radio jets of material composed of charged particles shoot outward from the magnetic pole of the black hole engine, creating long plumes that are thousands of light-years in their distance.

File:Black hole - Messier 87.jpg

Figure 1. The first direct visual image of a black hole in Messier 87, a supergiant elliptical galaxy in the constellation Virgo.

During the time in which Bell had started her graduate studies at Cambridge under Hewish, the new radio telescopes were meant to detect the scintillating behavior of quasars. As the light of a quasar hurls through ionized solar wind, the twinkling property manifests itself and could be spotted by their new radio antenna telescope. Bell spent her first two years as a Cambridge graduate student building the giant instrument by hammering and connecting wires. The new radio telescope instrument consisted of over four acres of land, 120 miles of cable wires suspended on about 1,000 wooden beams, and 200 hand-made transformers. See Figure 2. When the quasar-detecting machine was complete, Bell was the only person who operated the new instrument. She collected the data, which consisted of ink tracings on reams of paper, and she analyzed the machine’s output, a tremendous undertaking. The amount of data was immense, and Bell had to sort out any confounding artificial interference from the twinkling activities of the naturally occurring objects from outer space.

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Figure 2. Remains of the Interplanetary Scintillation Array at the Mullard Radio Astronomy Observatory, Cambridgeshire, in June 2014.

Shortly after turning on the new radio telescope in July of 1967, Bell noticed a strange signal in her reams of printed data from outer space. She called new tracings “scruff.” This scruffy data did not appear to align with either human-made interference or scintillating pulsars. Instead, Bell observed that the scruff appeared periodically, about every 1.3 seconds, from the exact location in the night sky of outer space. It was an ordered signal coming from the same patch of the night sky. Such regularly repeating scruff signals did not seem to belong to any previously known natural phenomena from space. See Figure 3 for Bell’s scruff pulsar data.

Bell and Hewish began systematically ruling out various artificial, manufactured sources, such as fellow radio astronomers, radio or TV broadcast signals, Earth-orbiting satellites, radar signals bouncing off the moon and entering their instrument, and even aberrant signals reflecting off nearby buildings with corrugated metal roofs.

File:Chart Showing Radio Signal of First Identified Pulsar.jpg

Figure 3. Jocelyn Burnell examined the chart in August 1967, showing the trace of the first identified pulsar, subsequently designated PST B1919+21.

The space signals appeared as intense pulses, regularly repeating every 1.3 seconds, too quickly to have originated from any known star at the time. Bell and Hewish called their new source, LGM-1 (for Little Green Men). She also nicknamed the signal “Belisha Beacon,” after the orange flashing lights meant to warn motorists of pedestrian street-crossings. While they felt that the space signal, though seemingly artificial, was likely not from aliens in outer space, they did rule it out, nonetheless. If the LGM-1 was an actual signal from a planet of beings revolving around another sun-like star, then the call should move about like a world in its orbit. The orbiting exoplanet should exhibit Doppler shifts during its “transmissions.” The LGM-1 pulse, however, showed no such Doppler effect, indicating that the signal could not have come from alien beings on an exoplanet orbiting their sun.

Instead, Bell and Hewish learned that their novel signal came from a star. This star source appeared to be distant from our solar system but well within the Milky Way galaxy.

The shortness of the pulsing transmission, only 1.3 seconds, suggested that the star must be relatively tiny, like a white dwarf star. Shortly after this historical pulsar discovery, Bell discovered three additional pulsars. Bell and Hewish, along with co-authors John Pilkington, Paul Scott, and R.A. Collins, published their novel findings in the prestigious journal Nature in February of 1968. Bell was the second author in the now-famous paper. The Nature article was the first published evidence for the existence of radio pulsars. Bell, a young graduate student, had played a significant role in the historic discovery of the legendary radio pulsars. This first pulsar, “Bell’s Star,” was first known as CP 1919, for Cambridge Pulsar with celestial coordinates 19h 19m. Later, Bell’s pulsar was updated with the designation PSR B1919+21. We now know that the object is 978.5 light-years away from Earth.

3) Now, for the layperson—what exactly is a pulsar?

A pulsar can be described as a rapidly spinning remnant of a dead star, called a neutron star. As the star rotates about its axis in precisely timed intervals, astronomers observe short pulses of radiation. Hence, they were pulsating radio stars, or pulsars, a term coined by Bell and Hewish. Neutron stars have strong magnetic fields and rapid spinning rates. In general, a neutron star is a compact and highly dense star consisting almost entirely of neutrons. These neutrons are tightly packed within the star’s diameter, the mass of which can resemble our solar system’s sun. However, a typical neutron star has a diameter of only about six miles (10 kilometers), whereas our sun is about 864,900 miles (1.4 million kilometers). A neutron star rapidly spins between 1.4 milliseconds to about 30 seconds per rotation, while our sun rotates once every 25 days.

We know that a neutron star forms when the core of a highly dense star collapses upon itself and undergoes an explosion of supernova proportions. What remains in the aftermath of a so-called type II supernova explosion is the spinning neutron star. When such stars go supernova, the material in the outer crust of the exploding star is sent away, leaving behind its neutrons that are tightly compacted into a spinning radiation-pulsing star.

The pulsars operate when charged particles are spiraling along the magnetic field lines of the neutron star, producing the radiation beam. As pulsars rotate, they emit a beam of radiation, sort of like a lighthouse with its rotating light shaft. When observers on Earth detect the radiation beam from a neutron star, we see the energy as a pulse, and when the pulsar is “off,” the radiation beam does not face Earth observers. The energy level of the radiation beams can vary, ranging between the radio, X-ray, ultraviolet, and gamma-ray intensities of the electromagnetic spectrum.

Pulsars are known to emit visible light. After the gases of the exploding supernova cool down, the visible light seems to fade but will shine with infrared radiation and pulse with perfectly timed radio waves. As such, pulsars are thought to be extremely precise keepers of time in our current universe, a so-called cosmic metronome.

When Bell and colleagues published their discovery of the first observed pulsar, it garnered a tremendous amount of attention. Soon additional pulsars were discovered, starting a new field of study in the astronomic sciences.

For her role in being the first person in the world to find the first pulsar signal ever, Bell would become one of the most famous graduate students in the history of stellar evolutionary science. See Figure 4.

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Figure 4. Susan Jocelyn Bell (Burnell), June 15, 1967.,_1967.jpg

4) Radio galaxies—what exactly are these?

Radio galaxies are a type of so-called active galactic nuclei, also called active galaxies, and they represent natural sources of radio waves from objects in outer space. See Figure 5. In general, there are several types of active galaxies. These active galactic nuclei differ by their intensity and orientations of dust rings and radio jets.

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Figure 5. Radio galaxy 3C98 labeled to show features. Made by uploader.

The radio galaxies are compact centers of galaxies with emissions of extremely wide radio wavelengths. The extreme luminosities, characteristic of radio galaxies, strongly suggest that non-star objects are responsible, such as supermassive black holes. Frequently, the emissions arise from two giant plumes, or radio jets, of a radio galaxy. A perpendicular accretion disc with a massive circular dust ring at the edge accompanies these jetting radio lobes. The accretion discs of dust are known to rotate.

The quasars represent the second type of active galaxy. These objects appear in the night sky as star-like points of light but are tremendously distant galaxies, as indicated by their red-shift characteristics. Quasars are thus galaxies with exceptionally bright cores, which emerge from giant dust rings. Quasars are thought to be supermassive versions of pulsars, with millions of densely packed stars forming galactic nuclei. It is believed such quasars are powered by giant matter-antimatter explosions and occur when gas and dust get sucked into the cores of black holes in the centers of galaxies.

The third type of radio galaxy is known as the blazar, also called a BL Lacertae object. The blazars are also star-like points in the sky but do not have significant spectral lines as the quasars do. Blazars are oriented towards Earth observers such that the radio-emitting plumes or lobes face us directly.

Lastly, the so-called Seyfert galaxy type has regular-looking spirals but is compact with light-emitting cores. The Seyfert galaxies are typically oriented in which the dust ring and accretion disc are visible but are less powerful than the quasars.

5) At first, Bell thought that space aliens, or “little green men,” as she called them—were sending signals to her—What was going on in reality?

Bell never seriously considered that her radio signals were from “little green men.” However, Bell and her colleagues did have to rule out such extraterrestrial activity to understand their discovery. It was a historical encounter with objects from outer space. Bell has described the pulsar discovery as sort of an accident. They were seeking quasars, which are enormously distant objects in outer space. Quasars were already known to astronomers. Instead, Bell had obtained contaminating noise signals that were closer than the sought-after quasars, and the annoying pulses got in the way of their attempts to study these quasars—at first.

As Bell examined the interrupting signals from outer space, she noticed that amongst the data, there appeared on her printed readouts various intense pulses, occurring periodically every few seconds. The timeframe of the pulsing radio waves was too short, suggesting that they did not come from any recognized stellar or planetary object. The pulses lasted only briefly, about 0.3 seconds per pulse, but they occurred precisely every 1.3 seconds. Furthermore, the energy beatings had no relation to the movement of the Earth.

Instead, the pulsations adhered to “star time,” a phenomenon known as sidereal time, as the pulse occurrences related to the activity of the stars and not the Earth.

As we mentioned above, Bell and Hewish called their new radio signal, LGM-1 (for Little Green Men). The idea, mused about only briefly and not to any serious-minded degree, was that perhaps the pulses were from aliens in space—little green men! The possibility that they were receiving messages from an alien civilization was intriguing. Bell and colleagues, however, immediately reasoned that their new radio signals were not from extraterrestrial beings from outer space. The astronomers understood that the signs originated from a neutron star and not necessarily from an exoplanet.

Further, the neutron star had likely gone supernova previously and, thus, could not harbor planets that might support living alien beings. As mentioned above, the LGM-1 signal did not move in a pattern like an orbiting planet around any star, as backed by the accompanying Doppler shift data. Bell and colleagues also ruled out the possibility that their novel radio signals were of Earth origin, as the emissions were mapped to locations far outside the confines of our solar system. They had systematically ruled out contaminating signals from Earth-derived sources and orbiting human-manufactured satellites.

When Earth- and alien-based civilizations were ruled out as sources of the energy pulses, the attention turned to the stars way beyond our solar system as a naturally occurring radio source. Bell and her astronomer colleagues would learn that the pulsating signal came from a neutron star. No one in the world had seen such a phenomenon, whether in space or on Earth. No one had ever imagined such an energy-radiating object could be possible.

As for the little green men, none have been found as of this writing. There are, however, active projects with the prime aim of finding bona fide alien signals from civilizations in outer space. The program is called SETI for Search for Extra-Terrestrial Intelligence, and scientists are still seeking evidence for such aliens. Bell Burnell had never been a part of SETI.

6) Her supervisor, Antony Hewish, won the Nobel Prize (for physics), and many felt that Bell was somewhat ignored. This episode was back in 1974. 

British astronomer Antony Hewish took the physics Nobel Prize that year for the discovery of the pulsars. He shared the prize that year with Martin Ryle, Hewish’s mentor, noted for his (Ryle’s) contributions to the invention of the so-called aperture-synthesis method. Hewish had designed the radio telescope instrument for detecting quasars. Together, Hewish and Ryle were recognized for their pioneering studies in radio astrophysics.

Jocelyn Bell Burnell did not ever share in the Nobel Prize. She was not even invited to the royal ceremonies. During that era in the 1970s and before, it would have been widely considered unprecedented for a student who did the work to share the Nobel Prize with the project’s principal investigator. However, soon after the Nobel nod to Hewish, critics pointed out a degree of unfairness in leaving Bell Burnell out.

She had, after all, built the machine, operated it, collected much of the data, been the first to pay attention to the pulsar’s signal, and was the first to suggest the neutron star as the radio source of the pulses. Yet, the Nobel went to Bell’s advisor, Hewish, who oversaw the lab and had designed the antenna device.

Bell had heard rumors that she would share the Nobel with Hewish. Solid evidence about the Nobel emerged when Bell and Hewish had been jointly awarded the 1973 Albert A. Michaelson prize. Then she learned that the prestigious accolade went to Hewish and Ryle.

Then or later, not even Bell Burnell seemed to be surprised about her omission. Bestowing the Nobel to lab assistants or students was not done in the day. In 1923, Frederick Banting took the Nobel for discovering insulin. Banting’s student, Charles Best, was not named in the official accolade. However, Banting had given Best a share of the Nobel award money. One might argue that it is not the fault of the Laureates for leaving out lab assistants or students when the choice of who gets the Nobel is determined. The Nobel Laureates are not, after all, routinely involved in the Prize nominations or the commission’s decisions.

Hewish, in his Nobel lecture, did name Bell. He gave her credit for connecting the cable network of dipoles in the antenna, keeping up with the paper flow from the machine’s recorders, and even bringing the new pulsing signals to his attention in the first place, in August of 1967. He even attributed Bell as providing a list of additional pulsars. Hewish further acknowledged that the discovery was a team effort, consisting of many Cambridge personnel.

Thus, while he seemed to have given due credit as he saw it during the Nobel festivities, Hewish nevertheless appeared to have mishandled the affair with news reporters afterward. When questioned by science reporters, Hewish had taken to naming only himself during his discussions, leaving out any mention of Bell or others. Hewish had to be prodded to provide additional details of the discovery if his team’s contributions were concerned.

Hewish’s dealings with the science reporters took a downturn. When specifically asked whether he or a graduate student of his who made the initial readings of the pulsar data, he seemed to have implied that he had taken the recordings himself, saying, “Oh, yes, I did.” He further stated that his graduate student was “doing observations, which I had designed,” keeping himself in the picture when conferring any credit to others.

Rather than blame the Nobel authorities for Bell’s omission, Hewing chose to defend their decision. He was not, after all, responsible for any of the selections made by the Nobel commission. At some point, Hewish became “fed up” with the “stupid business that Jocelyn did all the work, and I got all the credit.” Hewish went on record to elaborate that “If she’s [Bell Burnell] disgruntled about the Nobel, well that’s too bad quite honestly,” declaring that her work was not creative enough for a Nobel consideration. Nevertheless, in many circles, it is recognized that bestowing credit or recognition to additional contributors does not necessarily diminish those of the original recipient of the accolades.

Eventually, the controversy regarding who deserved credit for the pulsars then and the question of fairness (or lack thereof) faded away—until 1993, that is. Physics professor Joseph Taylor was given the Nobel Prize in physics because he discovered the so-called double pulsars, and his student, Russell Hulse, was named a co-Laureate! In the 1990s, both the professor and the student were given an equal share of the Nobel credit. Naturally, the old wounds from 20 years earlier regarding the discovery of pulsars and lack of equal credit were reopened. The issue was widely debated again. Taylor, who felt that Bell Burnell had been unduly overlooked concerning her contributions to the pulsar discovery, had generously invited her to his Nobel ceremonies. Anders Bárány, who was chair of the physics Nobel committee, gave Bell Burnell a replica of the Nobel medal as sort of a compensatory gesture.

Throughout this era, Jocelyn Bell Burnell had been benevolent about her exclusion by the Nobel commission. She had even been pleased in 1974 that an astronomer had taken the physics Nobel. Bell Burnell was proud to have been involved in such a historical, scientific discovery. To have been so closely associated with the pulsar discovery, however directly or indirectly, Bell Burnell related in the ensuing years that it had nevertheless provided her with “enormous enjoyment, [and] some undeserved fame.”

7) Bell Burnell held several positions—one at the Royal Observatory in England! Where else did she teach during her long career?

After receiving her doctorate from Cambridge, Bell Burnell taught and researched gamma-ray astronomy at Southampton from 1968 to 1973. Then, Bell Burnell spent eight years as a professor at University College London, concentrating on x-ray astronomy until 1982.

Bell was a tutor, adviser, examiner, and senior lecturer for the Open University From 1973 to 1987. Later, she worked at the Open University as a professor of physics while simultaneously studying neurons and binary stars and conducted research focusing on infrared astronomy at the Royal Observatory located in Edinburgh, Scotland.

Bell was the Dean of Science at the University of Bath from 2001 to 2004 and has been a visiting professor at such respected institutions as Princeton University and Oxford University.

While at Edinburgh’s Royal Observatory, she was head of the James Clerk Maxwell Telescope section, responsible for the British end of the telescope project based in Hawaii. Presently, Bell Burnell is a Professor of Physics and Department Chair, Open University, England.

8) Bell Burnell has also been involved in gamma rays, X-rays, infrared rays, and millimeter-wave astronomy. What do all these waves and rays have in common?

Bell Burnell used her expertise with the antenna to study each of these forms of electromagnetic waves. At Cambridge, radio astronomy was the area of investigation held by the newly minted Dr. Bell Burnell. But at Southampton University, she studied gamma rays. At Edinburgh, Bell Burnell had become interested in learning about infrared and millimeter-wave detection.

Each of these entities is a form of radiative energy and has specific electromagnetic radiation field characteristics. Thus, these electromagnetic components are all detectable on various antennas, each geared for the specialized detection of their specific wave energies. Another thing in common with these various electromagnetic fields is that technical devices can transmit their particular rays. For example, magnetrons were invented during World War II to be used as radar transmitters. Another example is the microwave oven, in which each range has its dedicated microwave magnetron. The substances that are heated in a microwave can serve as a sort of antenna. The third commonality to these energy waves is that they can be stored in gadgets colloquially called pillboxes. These apparatuses reflect the waves throughout the insides of the pillbox containers to keep the energy for later use. Lastly, these waves can be interrupted in their pathways through space, increasing their heat temperatures.

9) Although Bell Burnell never won the Nobel Prize, she did receive many other awards. Can you tell us about some of them?

Bell Burnell’s accomplishments have been recognized with numerous honors and awards. Among these awards include Commander and Dame of the Order of the British Empire in 1999 and 2007, respectively; the Oppenheimer prize in 1978; the 1989 Herschel Medal and the 2015 Royal Medal from the Royal Astronomical Society. Bell served as president of several institutions, including the Royal Astronomical Society from 2002 to 2004, the Institute of Physics, headquartered in London, from 2008 to 2010, and the Royal Society of Edinburgh since 2014. In 2018, she received the Special Breakthrough Prize in Fundamental Physics, which included a £2.3 million prize money that she entirely donated towards scholarships for women, minorities, and refugee students pursuing degrees in physics-related research. After her gracious gesture, the Institute of Physics later renamed this prize the “Bell Burnell Graduate Scholarship Fund.” In addition, Bell Burnell has honorary degrees from a wide assortment of universities.

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