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Cleo Loi: Groundbreaking Uni Astrophysicist

Charlotte Ward speaks with Sydney’s star science undergrad.

As the latest recipient of the Astronomical Society of Australia’s Bok Prize, Cleo Loi has become famous for the mark she made on modern radio astronomy last year in her Honours research. By applying novel insights to her analysis of data from the Murchison Widefield Arraythe new interferometer in WA that forms the precursor to the Australian Square Kilometre Arrayshe has made significant discoveries about the interaction between the plasma in the Earth’s ionosphere and the Earth’s magnetic field. Before moving to Cambridge for her PhD, Cleo spoke with Honi about her astronomical achievements.

So there were quite a few weeks earlier this year when the results of your Honours research really dominated science media, they were all over Facebook and newspapers. What was it like to have so much public interest in your results?

It was weird. And exhausting. I’ve never received that much attention for anything. I don’t even use social media. It was overwhelming because I’d be flooded by emails from people saying that ‘this is great’, but there were other crazy people who wanted strange, other details about me, which I refused to give them. But you got to see the general population’s response, not just scientists’.

With regards to my media involvement, I got to go on radio talk shows and do interviews. I recently got funded by the US government to do a trip to Washington to present to some of the staff at NASA and also the National Geo-Spatial Intelligence Agency, which sounds pretty scary, but they’re actually ok people. And yeah, giving talks all over Sydney as well as a presentation in Melbourne. So it’s incredibly tiring, but it’s been a good experience, to get that media exposure, because I’ve never had much of that before.

What drew you to astronomy in particular when you decided what research area you’d like to pursue in science?

So I’d actually done lots of research projects in different areas as an undergrad. Since my first year I’ve been involved with TSP (Talented Student Program) and I’ve also done summer projects and they’ve been astrophysics, high-energy physics, quantum physics, space physics. One thing that struck me about astronomy is that it gives you a range of experiences and lots of different skills that you need as a scientist. So astronomers do lots of programming, and programming is useful across all the sciences. There’s also exposure to data visualisation techniques and that’s something that’s used in other applications as well, such as medical imaging. And another skill for example is statistics, which is very useful.

You also get a lot of opportunities to think about the physics of what you’re studying because these are extreme environments and so the physics that goes on there is very different to what you’d find on Earth. So, basically, I’ve found astronomy to be one of the more all-rounded science subjects that I could go in to.

When you first started out on your Honours project at the Sydney Institute for Astronomy, what were your main research goals?

So the data that my supervisor uses is from the Murchison Widefield Array (MWA), which is a newly built radio telescope. And one of the problems for the MWA is the effect of the ionosphere because it causes distortions of the data. So what my supervisor wanted to do was investigate how bad the distortions are, and that ended up being the goal of my project: to see how much the ionosphere was causing the positions of radio sources in the sky to shift around and if it would cause any changes in their brightness. So these were things like what percent variation does it cause? And then you factor that into your error bars, for example, when you’re doing your transient searches. So that was the sort of information that my supervisor wanted me to get from analysing the data.

So moving on from those initial goals, how did you go about finding the discoveries that made your project so well known?

The discoveries were completely serendipitous. I had no idea that the Earth’s magnetic field could effect the plasma in that way, and I guess neither did my entire research group, because they’re concerned about things that are far beyond the Earth and don’t have that much knowledge of how the Earth actually works. So I went into this project almost completely cold about how the ionosphere behaves, and it was a real shock for me when I saw these tubular structures in the data.

How we actually did that was by looking at how the positions of the galaxies—background radio galaxies—were shifting around, and so for every one of thosuands of galaxies in the MWA images, we measured the positions, and then I thought one cool thing to do would be to plot the distributions in the sky with an arrow plot. So you’ve got one arrow where you’ve measured the displacement of a single galaxy, and when you do that you see that there are these organized patterns, like there’s this one strip of sky where all the galaxies move in one way and right next to that there’s another patch where all the galaxies more another way, and it’s this incredibly coherent striking pattern. And that was the discovery moment, when we first realized the magnetic field could do something so incredible to the plasma in the ionosphere.

So did you need to collaborate with people beyond astronomers to comprehend the data you had?

Yes we did. So the astronomers themselves couldn’t offer any advice as to whether this was something expected or not because this instrument is very new and it sees the sky in a different way, a much broader observation of the sky than anything—any other telescope that has been built. So they were as much in the dark as I was. So what we did was to consult the space physics group here at Sydney University who unfortunately don’t do as much stuff on Earth science so much as on solar science, so we then had to turn to other universities. We contacted people from La Trobe University then also the University of Newcastle, and finally the interpretation of the data as being these duct like structures came from a researcher from Newcastle. And that was a big help, being able to reach out to these other institutions and get their advice.

You mentioned that the MWA has a large field of view of the sky, what would you have not been able to do if you hadn’t been able to use it? Would other interferometers have been able to give you the same sort of data?

They would be able to make measurements at a similar sensitivity but their sampling would be much, much sparser. So the MWA can do detailed visualisations of the structure on tens to hundreds kilometres scales because it has such a wide field of view. So every galaxy essentially acts as a measurement point and you can see thousands and thousands of galaxies, and it looks like a starry night sky. That is your sampling distribution. Other interferometers have much narrower fields of view and so they can’t see very many sources. Their sampling is much sparser. They can only measure, let’s say, several tens of points at one time and that’s not enough to build up a nice image. Imagine you have an image that’s just ten pixels—you wouldn’t really even call that an image. But the MWA is the equivalent of a thousand or even several thousand pixels. That’s a proper image.

So how can astronomers use that understanding of the ionosphere to enhance future observations with the MWA?

So now we know that the MWA can be used to map out these structures, and so what astronomers next need to do is compensate, or use some kind of approach to compensate, for the distortions. One thing that these results have taught us is that the plasma structures in the ionosphere are not confined to just a single layer. And one idea that people have been toying with is to consider the ionosphere as a thin screen at a constant altitude and using that as your model for correcting distortions. But these tubes are not at a constant altitude, they’re highly inclined so they’re on a slope, and that means you can’t just use a simple thin screen to correct your observation. So it’s telling us that we need to be a bit cleverer about how we are eventually going to compensate for these distortions and that’ll be important for the project that the MWA is a precursor for, which is a square kilometre array. And that’ll suffer the same problems and possibly worse because it’s a much larger array and it will experience disruptions on a broader scale as well as down to the fine detail.

So after such a successful Honours year, what are you plans for the future in terms of research?

I’ll be starting my Phd at Cambridge in just a couple of weeks. And this will be with the Department of Applied Maths and Theoretical Physics, with the astrophysics group under that department. They study a number of things including tidal interactions, planetary formations and solar dynamo. So as for actually what my Phd project will be on, well I still have some time to lock that in, but right now the project they have down for me is on solar dynamo, so how the sun generates its magnetic field.

Would you have any advice for any high school or early undergraduate students who are hoping to pursue astronomy or physics research?

Well I think that the two main skills that you’re going to need all the time are programming and maths. Quantitative skills. So if you’re interested in pursuing this sort of research make sure you have a good foundation in those because they’ll serve you very well. Maths of course you can do in high school, so that’s something to think about if you’re still at school. And once you come to university, make it a point to start brushing up or learning programming skills. Because those are very important, not just for astronomy and physics, but for all sorts of science disciplines.