The Sciences

Discover Interview: Miles of Wire, Reams of Print-Outs, and a Giant Discovery

Jocelyn Bell Burnell worked through old-school equipment and old-school sexism to find the first pulsar—the beginning of an extraordinary life in science.

By Douglas ColliganDec 29, 2009 6:00 AM


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In her calm, deliberate way, astrophysicist Jocelyn Bell Burnell has always been in the business of changing worlds. Over a storied four-decade career, she has helped expand our understanding of the universe, caused people to rethink how Nobel Prizes are awarded, and used her stature to fight sexism in the world of science.

Burnell made her first scientific mark in 1968 as Jocelyn Bell, an unknown, 23-year-old doctoral student from Northern Ireland. After months of using the new radio telescope at the University of Cambridge, she came upon inexplicable, metronomically regular radio blips from isolated spots in the sky. Bell and her Ph.D. supervisor, Antony Hewish, concluded that the blips came from hitherto unknown objects, massive yet remarkably small. Because of their pulsed signals, these objects were dubbed pulsars. Soon after, pulsars were identified as rapidly spinning neutron stars, the remnants of supernova explosions; they weigh as much as the sun but are just a dozen miles wide. The discovery was so significant that the Nobel Committee recognized it with a share of the 1974 prize in physics—an honor that was presented to Hewish but not to the young woman who had made the initial observation, Jocelyn Bell. The snub made international news.

Time magazine hyped it as “A Nobel Scandal?” But Burnell was philosophical. “I believe it would demean Nobel Prizes if they were awarded to research students, except in very exceptional cases,” she later said, “and I do not believe this is one of them.... I am not myself upset about it—after all, I am in good company, am I not?”

During the 1970s and 1980s, Burnell went on to work in gamma-ray astronomy at the University of Southampton, X-ray astronomy at University College London, and infrared astronomy at the Royal Observatory in Edinburgh. In the 1990s she made a series of groundbreaking observations of the still-mysterious binary star system known as Cygnus X-3. All the while, her quiet achievements continued to break boundaries. When she became a full professor at the Open University of London in 1991, it doubled the number of female full professors of physics in the United Kingdom. In 2007 she was made a Dame of the Order of the British Empire by Queen Elizabeth in recognition of her contributions to science. Currently Burnell is a visiting professor of astrophysics at the University of Oxford; a professorial fellow at Mansfield College, Oxford; and president of the Institute of Physics in London, where DISCOVER caught up with her in her office.

Astronomy was part of your life from the beginning. Your father was the architect for the Armagh Observatory southwest of Belfast, right?Yes. The observatory has both a 200-year-old building and newer buildings. As observatory architect, my dad was partly concerned with the maintenance of them all. I used to go with him on site visits quite often, from age 7 or 8. I have memories of crawling through the rafters of the old building, trying to find where the leak in the roof was. I probably know the rafters of that observatory better than the astronomers who worked there.

So you were involved in astronomy before you even realized it.I don’t know how much influence that had, but I clearly knew of astronomy as a subject and an occupation. When I declared an interest in it, the staff showed me the telescopes and told me what it was like being an astronomer. And they thoroughly put me off. They were optical astronomers, and they worked at night. When they said to me, a teenager who loved her bed, that you had to be able to stay up at night, I knew I couldn’t. So I thought, “Hmm, maybe I can’t be an astronomer.” I then discovered radio astronomy and X-ray astronomy. These things were developing at that time. So I thought, “Right, then I can be a radio astronomer.”

That was your prime motivation—a good night’s sleep?[Laughs.] It was a large consideration. The ironic thing is that at the point where we were discovering pulsars, I was working quite a few nights because that was when the pulsar was in the telescope beam.

And radio astronomy was so new at the time that you had to build your own radio telescope at Cambridge.I was actually putting together the telescope. It covered four and a half acres. We put up over 1,000 posts and strung more than 2,000 dipole antennas between them. The whole thing was connected by 120 miles of wire and cable. We did the work ourselves—about five of us—with the help of several very keen vacation students who cheerfully sledge-hammered all one summer. It was a primitive type of telescope, as you would expect in the early days of the field. Radio astronomy was new then. It arose from World War II radar.

How did your radio telescope work?The output from the telescope appeared on four three-track pen recorders as a squiggly red line on moving chart paper. The telescope produced 100 feet of chart paper every day. One complete scan of the sky took four days, or 400 feet of paper. I was responsible for analyzing this. In the six months I operated the telescope, we recorded several miles of chart.

What led to your discovery of the first pulsar?My thesis project was to identify quasars, which are very distant, very energetic objects, and still quite mysterious. Some of the squiggles were what I was looking for, and some were radio interference. But there was another bit of squiggle that didn’t make sense. It took up about a quarter-inch out of 400 feet of chart paper. I think the first few times I saw it, I noted it with a question mark. But your brain remembers things you don’t realize it remembers. By about the fourth or fifth time I came across this signal, my brain said, “You’ve seen something like this before.”

I talked to my supervisor, Antony Hewish. We wanted this signal not to take up just a quarter inch but to be spread out so that we could see the structure. What we needed to do was to run the chart paper more quickly. We couldn’t run the chart paper at that speed for 24 hours a day—it would run out—so I had to go to the observatory each day at the appropriate time, switch to high-speed recording for five minutes, and then switch back to normal speed. I did that every day for a month. And there was absolutely nothing.

One day there was a lecture at Cambridge that I was very much interested in. I thought, “Stuff this; I’m going to the lecture.” Next morning when I went out to the observatory for the routine paper change, I discovered the source had reappeared, and I had missed it. So I didn’t dare go out for lunch or anything. I stayed at the observatory until that relevant time of day came and switched on the high-speed chart recording. As the chart flowed under the pen, the signal was a series of pulses. When I saw this, half of my brain was saying, “Gee whiz, it’s a pulsed signal,” and the other half was saying, “What do I do next?”

Was that an exciting moment?No, it was worrying, because we were not sure what this signal was. Tony was convinced there was something wrong with the equipment. And we had to know sooner rather than later, because my whole thesis was in jeopardy. After about a month we had sorted out that it wasn’t crossed wires and it wasn’t interference, and it wasn’t this and it wasn’t that. So what was it? It kept pulsing very, very, very accurately [every 1.339 seconds]. Now, if something is going to keep pulsing regularly and it’s not flagging, it must have big energy reserves. That means it’s massive. But it’s also small. When we say that, it’s because of the rapid repetition rate—we’re saying it’s small in diameter. We now know that pulsars are neutron stars, which are indeed very dense. They’re massive but small in dimension.

Your process of elimination is fascinating: You initially considered that the pulse could be a satellite, radio interference, a signal bouncing off a corrugated steel building?When you’re faced with something new, you have to find your own path across it, and one way is to think off-the-wall about what it might be.

Including the possibility that those pulses could be a signal beamed from another civilization?Radio astronomers are aware in the back of their minds that if there are other civilizations out there in space, it might be the radio astronomers who first pick up the signal. It didn’t make total sense, but faintly, just possibly. So we nicknamed that source Little Green Man. It was tongue-in-cheek. We weren’t serious, but we had to call it something.

When did you realize what you were actually dealing with?I was analyzing a recording of a completely different part of the sky and thought I saw some scruff. I checked through previous recordings of that part of the sky and on occasions there was scruff there. That scruff went through the telescope beam at about 2 o’clock in the morning. So at 2 a.m. I went out to the observatory, switched on the high-speed recorder, and in came blip, blip, blip, this time one and a quarter seconds apart, in a different part of the sky. That was great. That was the sweet moment. That was eureka.

How so?It couldn’t be little green men because there was unlikely to be two lots of them on opposite sides of the universe, both deciding to signal to a rather inconspicuous planet Earth. It had to be some new kind of source, some new type of star that we had never seen before. Later I found a third and a fourth as well.

Why did the discovery of pulsars have so great an impact?Because it was such a surprise and because the objects turned out to be so extreme. Nobody knew such things were out there. Pulsars later made black holes seem more plausible [by showing that a dying star could collapse to an extremely small size]. They opened up a whole new domain, a bit like when the Spanish conquistadores brought horses to South America. The native people had never seen horses! We had never seen anything like pulsars or neutron stars, and astronomers react not with fear—as the native South Americans did—but with excitement, delight, enthusiasm, amazement, fascination, and engagement to a startling discovery like this.

What was the response in the scientific community?Following the announcement, every radio astronomer who had access to the right equipment was observing the known pulsars and searching for more. A lot of research projects were disrupted as radio astronomers around the world commandeered anything suitable. Within six months the optical astronomers were joining in, particularly searching for a pulsar in the Crab nebula [the remains of a nearby supernova whose explosion was seen in A.D. 1054]. A group of X-ray astronomers who had previously observed the Crab nebula reanalyzed their data to see if they could have detected a pulsar in it, and they indeed found pulsations in their data. It became clear after about six months that these pulsars were rotating neutron stars. But there are features of pulsars that we still don’t understand, 40 years on. So the science moved very quickly, but it has also continued to be a lively field of research.

After the discovery was announced, you had a somewhat difficult experience with the press.Yes, that was very...interesting. They didn’t know how to handle a young woman scientist.

They asked Antony Hewish about astronomy, and they asked you if you had a boyfriend—How many boyfriends.

—and they compared your height with Princess Margaret’s.I got rather tired of these questions about what my height and breast and waist measurements were, so I said I didn’t know. Then the reporters tried prompting.

And then there was the Nobel Prize snub. Do you wonder how your life would have been different if you had won the prize?I have discovered that one does very well out of not getting a Nobel Prize, especially when carried, as I have been, on a wave of sympathy and a wave of feminism. I also was getting a lot of other awards, to some extent in compensation for not getting the Nobel. And that’s probably more fun because it means there are more parties. The Nobel goes on a week, but there’s only one party. And if you get a Nobel, nobody ever gives you anything else again because they don’t feel they can match it. So getting a Nobel could well have meant less fun over all.

There was a later Nobel Prize given for pulsar work, in 1993.Yes, the one that went to Russell Hulse and Joseph Taylor [for their work using a binary pulsar to study gravitational waves]. I went to that Nobel ceremony as one of Joe Taylor’s guests.

What was that experience like?It was great, probably more fun than going as a laureate. The recipient is forever having to stand up and say, “Thank you for this wonderful reception… [adding in a lower voice] which is totally the same as the two we had yesterday and the one we had the day before that. But never mind.” [Laughs.]

How many pulsars have been found to date?Probably pushing 2,000. It’s a hugely lively field. It keeps reinventing itself into something totally different, and whoosh—we go off in another direction.

There have even been some suggestions that pulsars could someday act as guide points for interstellar travel.Since each pulsar has its own distinct pattern of flashes and its own period, they could indeed be used one day as interstellar navigation beacons. But not yet, because we would need to attach a 100-meter [300-foot] radio telescope to a spaceship—or attach a spaceship to a 100-meter telescope. Some technological advances are required. Pulsars also provide us with very accurate clocks distributed through the galaxy, swinging beams around the sky like lighthouses and doing so with incredible precision. They have opened up experimental, as opposed to theoretical, ways to test Einstein’s theories of relativity. So far, the theories have checked out, but the pulsar astronomers are not done yet.

You have spoken often about the “leaky pipeline” phenomenon, referring to women who drop out of science careers after getting their Ph.D.s. Was there a time when you thought you might become part of the leak?Oh, yes, a lot of times, particularly during the phase when I was married and raising a family and following my husband around the country as he changed jobs. At the point when our son was born, I assumed I would suddenly turn into a normal female and would be quite happy staying at home and looking after a baby. I rapidly discovered that this assumption was wrong. To some extent I was trapped, in that I didn’t have a regular job. So I got a part-time tutoring job.

You tell an anecdote about how the Royal Astronomical Society was doing a series of lectures on British astronomers and did not want to include the 18th-century astronomer Caroline Herschel because she wasn’t good-looking enough.

That’s right. [Sighs.]

Did this happen recently?Not that long ago. And all my generation of women scientists have a host of stories about those kinds of thing. In Britain, in generations older than me, women were not expected to have careers. In generations younger than me, women do expect to have careers, or at least the option to have a career. It’s my generation that has been the turning point, and being at the turning point can be a bit rough sometimes.

What made you decide to speak out on the challenges facing women who want to have careers in science?I can remember when I was a full professor at the Open University, suddenly realizing that I was probably secure enough, established enough, that I could afford to start making trouble, thinking about other women and not just about my own career. I could start rattling the bars of cages. That was a very conscious decision, probably about 10 years ago.

What’s happening now is there is progress, although it’s slower than any of us would have wished. That may be just because we were too optimistic. And the other thing that’s happening at the moment is that four or five of the professional scientific and engineering bodies have suddenly got female presidents. The Geological Society has a female president. The Institute of Physics does too, and three of the engineering ones have or are about to have. I would love to think that the tide has turned.

Clearly, instead of being part of the leaky pipeline, you found your way back into the research world.Yes, but note that a number of my positions have been management, not typical academic ones. For example, at the Royal Observatory Edinburgh I headed the James Clerk Maxwell Telescope Section. I was also chair of the country’s biggest physics department at the Open University, and I was the dean of science at Bath.

On the research side of your work, what is the most exciting thing you have studied since your pulsar days?After pulsars, the research I am proudest of is on an X-ray source called Cygnus X-3, the third X-ray source discovered in the constellation of Cygnus. It is an X-ray emitting binary star near the edge of our galaxy, about 30,000 light-years away.

Some astronomers think Cygnus X-3 is a regular star orbiting a neutron star or a black hole. But nobody is really sure, is that right?Right. Infrared observations have shed some light on this obscure object. It shows bizarrely unique behavior in all wavelengths and appears to expand and contract at speeds greater than the speed of light. [The apparent faster-than-light speed, also seen in some quasars, is believed to be an illusion caused by our perspective on the object.]

In 1999 you singled out dark matter as one of the greatest mysteries in astrophysics. What do you think about it now, a decade later?[Laughs.] I’m still saying that. I have been saying for some time that we need a paradigm shift in cosmology, and I’m not alone in thinking it. But who knows what this new thing is If we knew, we would have Nobel Prizes right, left, and center. Cosmology does seem, to me, to be getting messy and is ripe for a change.

Do you think there is a revolution in the offing?Well, I think it’s due. Whether it’s in the offing is another question. 

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