Short Wave - This Radio Wave Mystery Changed Astronomy

Episode Date: February 26, 2025

In 1967 Jocelyn Bell Burnell made a discovery that revolutionized the field of astronomy. She detected the radio signals emitted by certain dying stars called pulsars. This encore episode: Jocelyn's story. Host Regina G. Barber talks to Jocelyn about her winding career, her discovery and how pulsars are pushing forward the field of astronomy today.Have cosmic queries and unearthly musings? Contact us at [e-mail]. We might open an intergalactic case file and reveal our findings in a future episode.Listen to every episode of Short Wave sponsor-free and support our work at NPR by signing up for Short Wave+ at plus.npr.org/shortwave.See pcm.adswizz.com for information about our collection and use of personal data for sponsorship and to manage your podcast sponsorship preferences.NPR Privacy Policy

You're listening to Shortwave. From NPR. Jocelyn Bell Brinnell knows that in space, just as in life, nothing lasts forever. Bigger stars at the end of their life explode dramatically. They hugely brighten up. They kick out a whole lot of gas and stuff into space. And the core gets kicked against, gets compressed, get shrunk right down. Massive stars more than 20 times bigger than R.C.

sun eventually collapse into black holes, infinitely small points of immense mass that we can't directly see. Then, there are smaller stars still bigger than our sun that don't fully collapse into black holes. They're known as neutron stars, because they're largely composed of one of the fundamental particles that we call neutrons. Those neutrons, they were created when the pressure from the explosion compressed the protons and electrons so tightly to Together, they combined. And so the core of the star becomes a ball that's about 10 miles across, typically, and spinning very rapidly.

A bit like the ice skater pulling her arms in spins faster. A chunk of a neutron star, the size of just a sugar cube, would weigh a billion tons on Earth. Or no big deal about the weight of a mountain. And because of that compression, these stars have much stronger magnetic fields. The strong magnetic fields keeps the charged particles constrained. And having lots of energetic charge particles confined to a small volume and whizzing around like fury will likely give you radio waves. Which is a good thing because...

Very, very few of them shine light. So we don't see them that way. We see them through the radio waves that they give out. These radio waves shoot out of the magnetic poles of some of these neutron stars as they spin. And on Earth, you'll only detect the radio waves if they happen to sweep across our planet, like the beam of a lighthouse. You only see them if they shine in your face or into your radio telescope. It looks like a pulse. That's why these particular stars are called pulsars.

Pulsar is an abbreviation for pulsating radio star. I'm Jocelyn Bell-Bernel. I discovered the first pulsar in 1967 and the second one and the third and fourth in 1968. Today on the show, Dr. Jocelyn Bell Burnell's story, how her astronomical discovery revolutionized an entire field of science. I'm Regina Barber, and you're listening to Shortwave, the Daily Science podcast from NPR. Jocelyn was just a teenager when astronomy took root. The real eureka moment for me was I was reading a book by Fred Hoyle where he was talking about these big galaxies, you know, 100,000 million stars. And Fred Hoyle in this book was talking about how these galaxies rotate, spin about their center.

And we're learning about this in school. And Fred's talking about these galaxies with stars rotating and what keeps them going around in a circle and not flying off. into space. I like, wow, I like this physics. I could be an astronomer and do this for a job. Life was just a blank page for her to fill in. And then somebody pointed out to me, the obvious, astronomers work at night. And as a teenager, in fact, even still now, I'm useless if I stay up all night.

They're thought, oh, I can't be an astronomer. I can't work at night. That is, until she found a kind of astronomy she could do in the daytime, radio astronomy. Because the sun doesn't dominate the radio sky, the way it dominates the light sky. So with a bachelor's degree in physics and a desire to be a daytime astronomer, Jocelyn starts graduate school at Cambridge, where she helps build the radio telescope that she used to detect the first pulsar. Although, at the time, that's not what she was looking for. I'm the person operating this radio telescope, looking for radio waves from stars and galaxies, particularly quasars, out there in space.

I can't honestly remember what the definition was at the time I started, except that they were intriguing and mysterious. At the time, astronomers had only ever detected about 20 of these elusive quasars. And I got the number up from 20 to 200. we now know that they're galaxy mass things, but they have a huge black hole in their center, which really dominates their behavior in many, many ways. And we probably know of thousands by now. So Jocelyn searches for these quasars by detecting radio waves with this telescope.

Basically, some of the light from distant stars reaches us as radio waves. And these antennae on the radio telescope focus those waves. The receiver detects those signals and turns them into data points on a page that look kind of like the marks on a polygraph. But in amongst all the data, there's a little signal that doesn't make sense. And the first couple of times I see it, I log it with a question mark and it doesn't make sense. Pass on. There's real work to be done. And as one of the only women, she was very concerned about proving she was capable of that real work.

I found Cambridge, when I was a grad student, really quite scary. everybody there seemed terribly clever, terribly confident, and I was quite sure they'd made a mistake admitting me. So I'm working very, very hard and thoroughly to justify my place there. But as she's collecting data, Jocelyn saw that odd signal again. And she recognized it. So she goes back to her miles of paper data and finds another signal that doesn't make sense.

And another. question mark. I've got five or six sightings of this thing, all from the same bit of sky. And that implies it's something astronomical. You're probably aware that the constellations you see in the night sky in summer are different from the constellations in winter. That's because the stars go round in 23 hours, 56 minutes, not 24 hours. Well, this funny squiggle, whatever it was, was keeping to the 23R 56 minute pattern.

So it was keeping its place amongst the constellations, whatever it was. But the pulses occupied only about a quarter of an inch on the paper. When she showed it to her thesis advisor, Anthony Hewish, he said she needed to enlarge it. And the way you get an enlargement is to run the paper faster underneath the pen. and it all gets spread out and enlargement. So I had to go out to the observatory at the time this thing was due to be observed, switch over to high-speed chart recordings.

And I did it for a month and nothing happened. My thesis advisor was livid. You know, it's been and gone and done it, and you've missed it. But she kept at it. And finally, she detected pulses again, this time in a string. One and a third seconds apart. And I went to the trouble of actually telephoning him to tell him the news.

And he was rather disbelieving. But he came out the next day, stood as I wired up for this special observation, checked that I was doing everything properly. And bless it, it performed again, and he saw it with his own eyes. And we could see immediately it's pulsing at the same rate as yesterday. For something to keep pulsing steadily, it has to be big. but it also had quite sharp pulses, which meant it was small. So that was our conundrum, along with what the heck could it be,

and why is it going at this very fast rate of one in a third seconds? Anthony Hewish presented the data to an audience of scientists. The data lit up the scientific community and other researchers switched gears, looking for more evidence of these pulsating radio waves. Soon, scientists concluded that the radio waves the telescope was picking up, were from a neutron star's poles. And so when spinning, they might sweep the radio waves across Earth. The discovery of pulsars amounted to a 1974 Nobel Prize in Physics for Antony Hewish,

which he split with astronomer Martin Ryle, who hugely advanced the sensitivity of telescopes. After Jocelyn made her landmark discovery, she married Martin Burnell. And her career took a turn. At that time, there wasn't any way of keeping my maiden name, so I lost that as well. and kind of lost my scientific reputation. And I married a person who had to move every five or ten years because of their job. And so my quote's career, note the inverted commas, has been really, really peculiar. Peculiar because with each move, she looked for a new astronomy job.

I was begging for a job at the nearest astronomy place to where my husband was about to go and work. and quite often got the kind of jobs you get when you go begging. And so the work wasn't always in radio astronomy, the field where she made her name unmarried. But it's actually worked out quite well. My curriculum vitae doesn't look too wonderful, but I have had huge fun working in many, many branches of astronomy, often landing in a new branch of astronomy just as it was about to boom. and I'm known for my work in several wavelengths. So, okay, I can live with that. Today, pulsars allow astronomers to measure cosmic distances, look for gravitational waves,

and search for planets beyond our solar system. The legacy, it's been a huge help to me through a rather difficult career that I've had the discovery of pulsars under my belt. our understanding of the universe keeps evolving. Clearly, pulsars are one key component of that. There's a lot more work to do on pulsars, and I think there's plenty more unexpected things to trip over.

If you keep your eyes open. Thanks, as always, to you listeners for tuning in, and we asked you for some of your favorite space facts. This is Lisa Latteu in Kyle, Texas. My favorite space fact is, is that it takes about three days to get from the Earth to the moon in a human spacecraft. I use that to help me imagine how much further away it is to other destinations. Hi, this is Rotem from Pittsburgh, Pennsylvania.

My favorite space fact is that Venus orbits around the sun faster than it rotates around its own axis. So a Venusian day is longer than a Venusian year. That's the kind of three-day weekend I can totally get behind. This episode was produced by Burley McCoy, edited by Rebecca Ramirez and fact-checked by Rachel Carlson. The audio engineer was Natasha Branch. Giselle Grayson is our senior supervising editor. I'm Regina Barber. Join us again tomorrow for more shortwave from NPR.