In Conversation with Dr Catherine Walsh

The Gryphon meets with one of Leeds’ resident astrochemists to discuss her eminent research, emerging technologies in astronomy, and the challenges facing women working in physics.

How do you go about detecting a molecule millions of miles away, in an entirely different solar system? That’s exactly what Dr. Catherine Walsh, University Academic Fellow in Astrochemistry, gets up to on her daily grind. Astrochemistry is the study of molecules in outer space, a field that according to Dr. Walsh “essentially operates at the interface between astronomy and physical chemistry.” Rock and roll.

“What I’m particularly interested in is how molecules are formed and destroyed in space, and in other astrophysical environments, like the material around young stars that will go into forming a planetary system. Some people aren’t really aware that a lot of chemistry happens in space, but we know that it is a very chemically rich environment.”

But why should we care about a load of molecules floating around space? Well, it may give us an insight into the formation of our own solar system, and even the Earth itself.

“We have these large molecular clouds that exist in interstellar space. The space between the stars isn’t empty, it’s full of these clouds of dust and gas that are full of molecules. These are very important environments, as the material that ends up coming into the star and forming the star itself originates in those molecular clouds. Some of that material will make its way into a circumstellar disc that orbits around the young star. This disc is very important, as it helps feed material on to the star that’s forming, but also any leftover material goes into forming a planetary system.”

Dr. Walsh and her colleagues are capable of determining the composition, temperature, and density of molecules in other solar systems from the comfort of their office.

“These objects are very tiny so we use a unit called arc-seconds in astronomy. If you imagine the entire sky is 360 degrees, just like a circle, then you can break that down into minutes and seconds, just like we do with time. This is the way that we map the sky. The discs around these stars are only a few arc-seconds, so really tiny. That means if we want to look for molecules in those discs that will go into forming planets, we need very high spatial resolution and observation. We are now able to map the composition of these discs that we know planets are forming within, so it gives us a view into the history of the solar system because our solar system will have formed from such a disc around the young sun.”

“Some people aren’t really aware that a lot of chemistry happens in space.”

You may be wondering how it is possible to view such tiny molecules so ludicrously far away. Telescopes. Big ones. And lots of them. Dr. Walsh and her colleagues make use of a relatively new technology called the Atacama Large Millimeter/Submillimeter Array, or ALMA for short, which uses the collective view of multiple powerful telescopes.

“It’s a huge instrument. The way that we do this is instead of just one telescope, which has a particular field of view, we make an array, so many, many telescopes. ALMA is such an array and its got 66 of these different telescopes. You add up all of the collecting area that each telescope has and then the resolution is set by the maximum distance between two antenna. The reason you can see with the resolution you can is because of the size of your pupil. So radio telescopes operate in the same way, but they have many eyes, which gives you a lot more information. So the maximum baseline of ALMA (the maximum distance between radio antenna) gives us very high spatial resolution. Enough that we can see molecules in discs around nearby young stars at about the same resolution as the distance between the planets in the solar system.”

Leeds is lucky to have such fantastic female representation in the Physics department. However, many women pursuing careers in physics feel like a fish out of water, males dominating the majority of classrooms. As a successful researcher, Dr. Walsh offers her advice to other women interested in joining the field: “When I have a lot of young people come and see us, I always ask them about the gender balance in their physics class and not a lot has changed unfortunately. So very often I hear the answer, ‘I’m the only girl in my A-Level Physics class’, and that was me 20 years ago. I think the best advice that I could give to young women who want to come into this field is don’t be put off. Once you get past the undergraduate degree and come into postgraduate study, the gender balance just shifts so much more. If you look in our PGR office, I think we’re close to 50% women, which is really nice to see. It takes a while to filter into lecturers and professorships, but hopefully that trajectory will stay. So don’t be put off because it’s a very rewarding career and I would love to see more young women joining us in the astrophysics community.”