Next big thing – understanding the formation of galaxies

I was born in Atlanta, Georgia. I loved doing a lot of things that kids do, playing outside with friends, riding bikes. I had a strange propensity for doing mathematics on foggy car windows. I enjoyed doing scientific experiments with chemicals in my closet, which probably nearly killed me.

I was part of a program called ‘Talented and Gifted Program’ in the Portland public schools, and they would pull us out of school to do science experiments for an afternoon. This was so much fun. So I remember dissecting a pig’s heart. I remember taking apart a cow’s eyeball and taking the lens back home with me. I remember dissecting a dog shark. But it was not until I hit high school that I found that what I really liked was doing the physics types of things.

I went to Oberlin College ((the first college in America to adopt a policy to admit black students (1835) and the first to grant bachelor’s degrees to women (1841) in a coeducational program-Ed) and I started out studying both physics and in maths, and French. I found that physics was a little bit more exciting, but French has remained a passion throughout my life.

In my final year I was offered the chance to come to Australia with one of my professors. It was the perfect time to do my research project with the CSIRO Parkes telescope.

Parkes is a full body experience. You hear the telescope moving above, you feel the building vibrate a little bit and you know that when you are telling the telescope to go to a particular position, you are in control of this most powerful radio telescope in the southern hemisphere and you’re pointing it at the one thing that you want to look at.

So radio astronomy is just another branch of astronomy, whereas we’re used to astronomy in general, looking with our eyes and visual wavelengths. In radio astronomy we look at the wavelengths where radio waves are. The radio telescope is just like any other telescope. It reflects the radio waves to a place where we can receive them to make images of the sky at radio wavelengths that we could never see with our own eyes.

Radio wavelengths, tell us about a different set of processes that exist in the universe from what you tend to see with optical. So when you look out at the night sky, you see stars, you see a little bit of dust in between the stars or that blocks the stars, but what you’re really dominated by is the stars. But in radio astronomy what we tend to see is the gas between the stars.

Atomic hydrogen is the very simplest atom in the universe, one electron, one proton emits a radio wave at 2cm wavelength, and we can use that to map out the structure of galaxies, find galaxies across the universe, and hopefully with the SKA, we’ll even see the structure of the universe when the very first stars appeared.

Read about how SKA is searching galaxies

Yeah, so atomic hydrogen is the most fundamental building block of the universe. Everything that we see started out coming from hydrogen. If you look up at the night sky, you see a dark patch that’s blocking out all of the stars. That’s a patch that has molecular gas and will probably form stars in its future, but in its past it was just plain old vanilla hydrogen that was floating around inside the galaxy.

But the brilliant thing about atomic hydrogen is it’s like a radio station and if that hydrogen is moving away from us, it changes its pitch as it moves to a different frequency. So by looking at atomic hydrogen and looking at the frequency with which we measure hydrogen, we can tell whether the gas is moving away from us or towards us.

It acts like smoke particles in a room. You can tell if somebody opens a door and the smoke drifts one direction and they open a door on the other side and it drifts the other way. Hydrogen does exactly the same thing inside galaxies.

So if a star explodes, it pushes all the hydrogen one way and we can see it move away from where that star exploded or we can see it moving as it collapses into a molecular cloud.

I’m trying to understand the atmosphere that is our galaxy, how the gas within it moves around, how it’s formed stars, how it reacts to big stars around it.

I’m looking at chimneys of gas where gas goes flowing out of the galaxy altogether so that it interacts with the circumgalactic medium. And I’m also looking at how our galaxy is interacting with its nearby galaxies.

Magellanic clouds, which are some of our nearest galaxies, are coming into the Milky Way and as they do all their gas strips off behind them and looks like a big huge comet tail. It is something that we can trace in atomic hydrogen.

The Milky Way has been continuously creating stars for more than 11 billion years. And in order to continue creating new stars, it needs to continually receive fresh gas.

But we think that magnetic fields play a role in confining where gas can move.

So one of my research questions is how do magnetic fields interact with galactic scale gas that’s coming in to our own Milky way?

The answers on how magnetic fields and gas interact are probably five to 10 years away. This is a new field of research. It’s something that we’re just really getting into and we’ll take off with the square kilometre array.

It’s relatively easy to see the stars traced out, but the gaseous arms of galaxies extend out twice, three times as far as the stars do. And what I found in the Milky Way was a gaseous spiral arm that was stretching out in a far outer part of the galaxy that we’d never noticed before.

It’s sort of disappointing that I never had an aha moment of discovery. It was never a moment where I went, I’ve got this.  I always wondered if that could be right. Is that really a spiral alarm? No. Surely somebody would’ve thought of that before. Maybe it’s a spiral arm – it must be something else. And it went on and on with my confidence gradually building that there was no other way I could explain this feature then by this quite simple idea that it had to be a new spiral arm that we’d never seen.

But I don’t think I was fully convinced that I’d found that spiral arm until a few years later, another team in Japan found molecular gas associated with that and that molecular gas is a sign that there might be a few stars that could form out there. And I think at that point it gave me the confidence that that was really was the structure I thought it was.

I think the big questions that I’d like to see answered in the next 10 to 15 years are things that are actually not my own specific research. I’m working on understanding how our own galaxy works, but it’s just one galaxy in the scheme of billions of galaxies.

I’d like to see how those galaxies first started to form the very beginning of the formation of galaxies. How did they come together out of the gaseous flow of the universe and whether magnetic fields were right there from the beginning or came along a bit later.

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