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How stars are born

This PhD is investigating why we have the particular stars and galaxies that we do.

Do you ever gaze up at a starry night sky, and wonder where those beautiful twinkling stars began?

Stars are born within clouds of dust in space. Gravity coalesces the gas and dust in these clouds into dense clumps over millions of years. The material at the centre of these clumps begins to heat up until eventually, through the nuclear fusion of gas, a star is born. 

The material that does not become part of the star may form into planets and objects that orbit around it – like Earth around our sun.

But there is a larger force at play in the Universe that dictates the fate of the stars… black holes. 

When most people think of black holes, they think about big voids in space that suck in matter and light. That’s not wrong, it’s just not the whole story. Black holes also release a lot of energy, which plays an important role in the formation of stars in galaxies.

PhD student Ross Turner has been fascinated by black holes since he was an undergraduate.

His research looks at how much energy very massive black holes release, which has a big effect on galaxies. 

I look at stars to try and understand the machinery going on in the background. Why are those stars there? I’m trying to understand the physics behind why we have the galaxies and stars we do.

“I look at how much energy is released from the black hole through high-speed jets of particles that plume out into the surrounding galaxy. Particles in these gas plumes emit lots of radiation in the form of radio waves. I can observe this radiation to measure how big these plumes are, and how bright they are.”

Then it comes down to the maths.

“I’ve got a whole lot of mathematical models that can show what the plume would look like, if I put in a certain amount of energy, over a certain amount of time.

“If you have a whole lot of simulations for different amounts of energy over different amounts of time, you can work out what it would look like and you can compare it to what you’ve observed.”

These simulations are very important to understand how the galaxies in our universe formed and how the stars and gas in them has changed over time. 

If there is a giant cloud of gas, normally it will collapse due to gravity, because any two particles are gravitationally attracted to each other. They will go into a clump and eventually form a star. This can only occur if there is not too much energy within the cloud.

“If a black hole is releasing a lot of energy into that cloud, then the particles move around quickly and just shoot past each other, which stops them condensing into a clump and forming a star. 

If you measure the black hole and it’s outputting a whole lot of energy, you know you won’t have any stars forming. If you don’t have much energy, you’ll have stars forming. So you can sort of work out what’s happening with galaxies. Will they form a lot of stars, or won’t they?

How do you get a career studying the stars?

“When I was little my parents got me books about space. I had about four or five books that I read all the time, trying to learn about the planets. When I went to school I got really interested in maths- that’s what I was best at."

Both of Ross’ parents studied maths and physics.

“Maths and physics are quite related. I oscillated between the two, trying to figure out which I liked more. But with physics, I got the best of both worlds. I can use maths to solve all these interesting problems.”

Ross studied a Bachelor of Science majoring in Physics. 

By the time he reached his Honours year, Ross had already been the lead author on a research paper; a massive feat for an undergraduate. Now in the final year of his PhD, he is clearly still pretty keen on physics.

Ross is keen to take up a postdoctoral position after he finishes his PhD, but says he also likes teaching.

“I like being able to engage the students, teaching and helping people. It’s also a good break from being in your office working all the time. So it’s both selfish and altruistic.

“When we have tour groups through our observatory, we tell the kids that to do the cool stuff, they need to study their maths and computer programming,” he said.

“It’s great to be able to inspire the next generation to study physics."

Interested in conducting your own research? Apply now to become a research student.