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.
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.