Star Stuff: Pulsars are cool but Jocelyn Bell Burnell is even cooler

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Nov 30, 2017

Star Stuff is a weekly column by rocket scientist & astrophysicist Summer Ash highlighting some amazing things happening every day on and off the planet, especially great science done by and/or for women. She harnesses her science communication powers to smash the patriarchy and advocate for equality and inclusion across all time and space. Throwdowns with pseudoscience may occur.


This week marks 50 years since Professor Dame Jocelyn Bell Burnell discovered pulsars with a telescope she built to study an entirely different class of objects (quasars) while she was only a graduate student at the University of Cambridge. There is so much awesome in that sentence that I don’t even know where to begin. Plus, it’s hard to get past such a magnificent title as “Professor Dame,” or my preferred version: “Doctor Dame.”

Pulsars are the surviving remnants of supernova explosions, rapidly spinning neutron stars emitting beamed columns of light along one axis while rotating around another axis. They produce a “lighthouse” effect as they spin whereby we see a pulsing light when the beam is tilted in our direction. While the average lighthouse light rotates once every few seconds, pulsars can spin at rates ranging from roughly 150-1000 times a second! Oh, and did I mention they are roughly the size of Los Angeles?

Pulsar animation showing spinning neutron star and the "pulse" signal received on Earth. Credit: Jen Christiansen, Scientific American. 

The name pulsar is a portmanteau of "pulsating radio star" because they were detected first by the radio telescope built by Bell Burnell and her supervisor Anthony Hewish while she was studying at the Cavendish Laboratories in Cambridge. The telescope, known as the Interplanetary Scintillation (IPS) Array, looks more like a field of wires rather than a dish because it was designed to detect very low radio frequencies, on the order of 80 MHz. Bell Burnell was actually hoping to observe quasars (another astronomical portmanteau, for "quasi-stellar") as her thesis was on "the measurement of radio source diameters.”

Bell Burnell spend two years building the IPS Array along with several other students in the department. She was primarily responsible for the cables, transformers, and some connectors. “It was indeed normal for PhD students to be involved in the construction of radio telescopes -- indeed we were presented with a set of tools (screwdriver, pliers, wire cutters, etc!) as we joined,” she told Hannah Middleton in LIGO Magazine’s 11th issue. The completed telescope covered roughly four acres (that’s an equivalent size to almost 60 tennis courts).

Interplanetary scintillation array at Mullard Radio Astronomy Observatory, Cambridge, England. Creative commons.

Once the telescope was up and running, Bell Burnell’s job was to analyze the data. Back in 1967, the data did not come out as 1s and 0s and was not read by a computer. Instead, the output of the telescope was in the form of a line on graph paper, 30 meters of it per day, all of which Bell Burnell examined by eye. When she found what later turned out to be the first pulsar, it was in the form of a messy squiggle in a half centimeter of one day’s data. The signal was compressed because of the rate at which the telescope was set to recording the data. With her supervisor’s permission, Bell Burnell switched to a high-speed recorder to spread the signal out over 15-20 centimeters instead. What she found was a spike that repeated every 1.3373 seconds and eventually an entirely new class of objects.

Professor Dame Jocelyn Bell Burnell describes how she discovered pulsars.

Born in Northern Ireland in 1943, Bell Burnell had her fair share of struggles prior to becoming a successful astrophysicist and source of inspiration to so many women in science. She failed her 11-plus exam, a test administered to see if 11-12-year-olds should go on to a elite secondary school, an average secondary school, or a vocational school. Her parents sent her off to a Quaker boarding school, where she got interested in physics. She went on to study at Lurgan College, but was only allowed to pursue physics after her parents (and others) protested the school’s policy prohibiting girls from doing science. She became the only girl in a class of 49 boys at a time when it was acceptable for them to heckle her constantly. “There was a tradition among the students that when a female walked into a lecture theatre all the guys stamped and whistled and called and banged the desk,” she told the Belfast Telegraph. “I faced that for every class I walked into for my last two years."

Unfortunately, the hurdles she faced as a woman in physics didn’t end there. Once Bell Burnell and Hewish confirmed their discovery was not an error in the data, they went on to find several more pulsars and published their results in Nature in early 1968. Less than eight years later, Hewish and his colleague, Martin Ryle, who was a pioneer of radio telescopes, were jointly awarded the 1974 Nobel Prize in Physics for their advances in radio astrophysics -- Hewish for pulsars and Ryle for aperture synthesis (combining data from multiple radio telescopes). Bell Burnell’s contributions were not mentioned.

 

This year marks 43 years since the Nobel Prize was awarded for the discovery of pulsars, and yet Bell Burnell is still often treated as an afterthought by the establishment. On her behalf (as well as others’), many of us are frustrated with the Nobel process and the standards it sets for science. While Bell Burnell has never expressed any outrage over this slight, talking to the BBC in 2006 as reported in The Guardian, she reflected:

"In those days, it was believed that science was done, driven by great men ... And that these men had a fleet of minions under them who did their every bidding, and did not think. It also came at the stage where I had a small child and I was struggling with how to find proper childminding, combine a career, and before it was acceptable for women to work. And so I think at one level it said to me 'Well men win prizes and young women look after babies.'"

Bell Burnell has gone on to both look after her baby and win her fair share of prizes. She has become and advocate for women and diversity in science. She became the first female president of the Institute of Physics (IoP) in 2008 and went on to become the first female president of the Royal Society of Edinburgh in 2014. In 2012, she chaired a working group for the Royal Society of Edinburgh whose goal was to increase the number of women in science, technology, and mathematics in Scotland. And as of 2016, the IoP’s Very Early Career Female Physicist Award was renamed the Jocelyn Bell Burnell prize in her honor.

We now know of over 2,600 pulsars in the Milky Way and beyond, and we can use them to probe a variety of physics, from supernovae to dark matter to relativity. Pulsars have such precise timing that they are effectively clocks ticking off time, each with their own unique pattern. A mere five years after their discovery, Frank Drake and Carl Sagan were already taking advantage of their precision to create a map of our location in the galaxy with respect to 14 nearby pulsars. This map was engraved on both the plaques for Pioneers 10 and 11 and a few years later on the cover of the golden records for Voyagers 1 and 2.

Even though supernovae had been know about for centuries, pulsars really drove home the point that stars change and evolve. Bizarre objects like pulsars and black holes existed theoretically prior to 1967, but the reality of them was a big shift in modern astrophysics. The discovery of pulsars enabled scientists to take black holes a lot more seriously than they were at the time. And now, 50 years later, we not only have entire physics and astrophysics departments dedicated to black holes, but they have opened up an entirely new way of studying the universe via gravitational waves.

I’ll leave you to reflect on both pulsars and the amazing Doctor Dame Bell Burnell in your own time, but before you go, I encourage you to listen to her reflect on pulsars and our understanding of the universe.

Professor Dame Jocelyn Bell Burnell on pulsars, gravitational waves, and how science works.