PhD student maps Milky Way’s magnetic field for first time

When it comes to studying the Milky Way Galaxy, there’s more than meets the eye — quite literally.

Astronomy is one of the oldest natural sciences. For hundreds of years, we’ve been able to study the movement of the planets because we can see matter moving, which is dictated by gravity.

But there's an influencer in our galaxy other than gravity: the magnetic field. It’s a relatively new discovery (by new, think the last 100 years) and scientists still have a lot to learn about it.

Rebecca Booth, a third-year PhD student in physics and astronomy, is one scientist who is dedicated to learning more about the Milky Way’s magnetic field. Booth was the recipient of both a Vanier Canada Graduate Scholarship, one of the most competitive and prestigious graduate awards in Canada, as well as a Killam Award for her research on creating a three-dimensional map of the galactic magnetic field — quite the task for something that is impossible to see.

“It’s this huge magnetic field, and we don’t know what it looks like,” says Booth, BEd ‘07, MSc ‘21. “One of the biggest challenges in astronomy is you can’t just go there and measure it with an instrument because the galaxy is so big.”

Using a radio telescope to create the first map

The galactic magnetic field is impossible to see with a standard optical telescope. The only way to map the magnetic field is through radio astronomy, which measures radio waves.

“We’re trying to measure the galactic magnetic field, but we can’t just look at it because magnetic fields don’t give off light,” says Booth. “Instead, we have to look at how the magnetic field affects light that passes through it.”

From that information, Booth and scientists from around the world are attempting to create a three-dimensional map of the magnetic field. Although study in this area is relatively new, Booth and her colleagues do know the magnetic field plays a vital role in galactic dynamics, including holding up the galaxy from gravitational collapse, the formation of stars and potentially even the formation of the entire galaxy.

“Understanding galactic dynamics helps us understand fundamental things like where the galaxy came from, how it formed and how it’s going to continue to develop,” says Booth. 

A homegrown telescope

To measure the radio waves from the galactic magnetic field, Booth and her supervisors, Dr. Jo-Anne Brown, PhD, and Dr. Tom Landecker, PhD, use a telescope at the Dominion Radio Astrophysical Observatory (DRAO) in central British Columbia. Their work is part of the Global Magneto-Ionic Medium Survey, an international effort by 32 scientists from eight countries to map the polarized radio sky.

Booth emphasizes that not many people know that Canada is a world leader in radio astronomy. Having this “homegrown” telescope in Western Canada means skills are being built locally that can contribute to fields outside of astronomy. After all, the techniques used in radio astronomy ended up helping the development of Wi-Fi — something most of us can’t imagine living without.

“Astronomy builds capacity. The work I do in imaging is working at an extreme level with difficult conditions, because we’re trying to image something super far away that’s fairly faint,” she says. “The imaging techniques we develop can then be applied in other fields, like medicine, geology and beyond. It’s important having that work locally because we’re building the talent and the techniques in our community.”

Going to the DRAO is a unique experience in itself. The facility is inside a federally protected “radio quiet zone,” which means there is no cell service or Wi-Fi and electronic devices are not allowed. Any of these things could interfere with the radio signals or damage sensitive equipment.

Instead of being able to Google questions she has about her research, Booth carries around a notepad and pencil and writes them down for later — not always the most intuitive practice for somebody who grew up with the internet at her fingertips. Yet, she thinks the lack of technology at the DRAO is the reason why such good work is happening.

“It’s part of why the community of people who work there are so collaborative and welcoming. It invites a certain type of person who enjoys working in that kind of space,” Booth says.

From teacher to astronomer

Booth has known she wanted to be an astronomer since she was a young child. Yet, her path to becoming one hasn’t been as straightforward as her childhood dreams. After completing an undergraduate degree in physics, she went on to get a bachelor's degree in education from UCalgary and then taught high school physics for 12 years.

She doesn’t see her teaching career as a mistake, though, more of a sidetrack that allowed her to dig deep and discover what she really wanted to do.

“Teaching was a really wonderful experience, I met kids that were some of my favourite people I’ve ever known,” she says.

There is no road map for following your gut and heart to find the right career, just like there’s no road map for the kind of exploratory science Booth is doing. Although some might find that challenging or intimidating, she sees this as exhilarating.

 “We talk about the scientific method where you come up with a hypothesis and design an experiment and then everything goes well and you find out what you wanted to know, but sometimes you design the experiment and then you find out what the hypothesis should have been,” Booth says.

“What we’re doing is exploratory science. We don’t necessarily know what we’re going to find out. That’s the best part of my work.”