Science & Technology

Pulsars Are One of Our Best Tools for Understanding the Universe

As far as astronomical objects go, pulsars are incredibly handy. These predictably pulsing beams of light have helped us better understand neutron stars, discover exoplanets, and prove Einstein's theory of general relativity. But when the 1967 Nobel Prize in Physics was awarded for their discovery, their discoverer wasn't actually mentioned. Thankfully, she finally got her recognition in 2018 — and the prize may help young scientists the world over.

"I Wasn't Going to Walk Away"

By the time she reached graduate school, Jocelyn Bell Burnell had already faced her share of sexism. The local grade school wouldn't let girls study science, so her parents protested until she was allowed in with the boys. Then she failed the standard British exam that would have let her go to college — not because she did poorly, but because those in charge had artificially raised the required passing score for girls to keep them from pursuing higher education (a practice that isn't yet behind us). So once she received her degree in physics and was accepted to Cambridge University as a graduate student, she was understandably unsure of herself and experiencing more than a bit of impostor syndrome.

But Bell credits this feeling of being an outsider for her fresh viewpoint and dogged work ethic. "I'd had quite a fight to get there, and I wasn't going to walk away from it," she told Ars Technica. Immediately after her Cambridge team finished building a new radio telescope at the Mullard Radio Astronomy Observatory, they started taking data, and Bell Burnell was charged with analyzing roughly 700 feet of paper records every week to spot unusual signals.

It was no more than three weeks later that Bell Burnell found her first unusual signal: a faint pulse that disappeared and reappeared every 1.34 seconds on the dot. The team tried to explain it with natural sources or manmade interference, and one by one every explanation was ruled out. She and her thesis advisor Antony Hewish jokingly dubbed the object "LGM-1" for "little green men." But soon, Bell Burnell spotted more of these pulsing signals, which she and Hewish dubbed "pulsars."

A Cosmic Swiss Army Knife

What Bell Burnell found proved to be an unimaginably useful tool for understanding our universe. Pulsars are a type of neutron star, which is the super-dense core of a massive star that exploded but didn't have quite enough mass to turn into a black hole. Neutron stars are the densest objects known to man and possess powerful magnetic fields. Pulsars, then, are spinning neutron stars that emit powerful beams of radio waves from their magnetic poles. It was this beam that Bell Burnell detected in that first unusual telescope reading.

Here's why that's so important. Because they're such extreme objects, neutron stars are nature's physics laboratories. They experience extreme gravity, a density beyond that of atomic nuclei, and incredibly strong magnetic fields, none of which we can recreate on Earth. The timing of a pulsar can help us precisely measure these properties.

If we know the properties of the pulsar, then we can perform unique experiments involving gravity. Albert Einstein's theory of general relativity says that, among other things, massive objects cause a distortion in the fabric of the universe (aka spacetime), which is felt as gravity. So far, this theory has been incredibly successful in predicting what we see in the universe, but it's not the only theory out there. Some say that extreme objects like neutron stars might be special, and experience more gravity than Einstein's theories predict. The predictable behavior of pulsars helps scientists put this to the test — and recent experiments show that Einstein's theories are still the right ones.

That same precision is what helped astronomers confirm the discovery of the very first planets outside our solar system more than 25 years ago: Those three planets were orbiting the pulsar PSR B1257+12. And in the future, the hope is that pulsars will help us confirm another aspect of general relativity: the prediction that the motions of the masses in the universe should cause disturbances of spacetime in the form of gravitational waves. The Earth-based instrument known as LIGO has already detected higher-frequency gravitational waves from the collision of smaller black holes and of neutron stars, but pulsars may help us find the low-frequency gravitational waves that should be produced by merging supermassive black holes.

Well-Deserved Recognition

Bell Burnell received her Ph.D. in 1969, and the 1974 Nobel Prize in Physics was awarded for the discovery of pulsars. But Bell Burnell wasn't mentioned, since she was just a graduate student when she made the discovery. Instead, the prize went to her adviser, Antony Hewish, and the astronomer whose concepts the new telescope was based on, Martin Ryle. At first, Bell Burnell said she didn't mind. "I believe it would demean Nobel Prizes if they were awarded to research students, except in very exceptional cases, and I do not believe this is one of them," she said in 1977. Today, however, she admits that she didn't feel empowered to fight it back then. When she was a postdoctoral student, she says, she "was not in a position to rock boats, and in need of support from senior men."

In 2018, Jocelyn Bell Burnell got at least some of the recognition she deserved: She was awarded a $3 million Special Breakthrough Prize in Fundamental Physics. But she's not keeping the money. Instead, she's using it to fund women, underrepresented minorities, and refugee students to become physics researchers and counter the unconscious bias that she believes still plagues scientific research. "I don't want or need the money myself and it seemed to me that this was perhaps the best use I could put to it," she told BBC News.

"I found pulsars because I was a minority person and feeling a bit overawed at Cambridge," she said. "So I have this hunch that minority folk bring a fresh angle on things and that is often a very productive thing. In general, a lot of breakthroughs come from left field." Jocelyn Bell Burnell changed our understanding of the universe with her discovery, and now she's helping more people like her do the same.

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To see the charmingly illustrated achievements of pioneering women in science, check out the New York Times bestseller "Women in Science: 50 Fearless Pioneers Who Changed the World," written and illustrated by Rachel Ignotofsky. We handpick reading recommendations we think you may like. If you choose to make a purchase, Curiosity will get a share of the sale.

Written by Ashley Hamer September 7, 2018

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