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Prof. Orsola De Marco is a Professor at Macquarie University and Deputy-Director of the Astrophysics and Space Technologies Research Centre at Macquarie University in Sydney. She obtained her PhD at University College London as a Perren Scholar, after which she was a Swiss National Science Foundation research fellow at ETH Zurich, a FUSE Fellow at University College London and Asimov Fellow at the American Museum of Natural History in New York City. She was an ARC Future Fellow. Her research focusses on stellar interactions and how they alter the structure and evolution of stars in multiple systems.
Transcript:
Brendan: Welcome to the Astrophiz Podcasts. My name is Brendan O ‘Brien, and first of all, we would like to acknowledge Australia’s first astronomers, the Aboriginal and Torres Strait Islander people, the traditional owners and custodians. of the land we are on. This episode is produced on Yorta Yorta and Wurundjeri country of the Kulin Nation.
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Today I’m at the ‘Transients Down Under’ Conference in Melbourne, Australia, known affectionately as the TDU Conference.
It’s the first face-to-face astrophysics conference to be held in Australia, since COVID hit us back in 2020. And it’s great to see a couple of hundred delegates and invited speakers here meeting and sharing their research in person in such an exciting environment here at the Swinburne University of Technology … and a big shout out to Ashley and Jeff who allowed me to attend and record some interviews.
I’m recording in a repurposed planetarium. which is very ‘live’ with lots of hard timber and glass surfaces.
Today I’m here with Professor Orsola De Marco, who is a Professor at Macquarie University and Deputy Director of the Macquarie University. Astrophysics and Space Technologies Research Center. And I’m also very excited to be with her here on Wurundjeri land at the Transients Down Under Conference.
Orsola was born in Verona in Italy, the hometown of Romeo and Juliet, and she grew up in beautiful Bologna. She left home to finish high school at the United World College of the Adriatic in Trieste northern Italy, and then, after a brief interlude, teaching sailing in Scotland, moved to the University College uf London to study astronomy and stayed on there, and obtained her PhD … after which she was a Swiss National Science Foundation Research Fellow at ETH Zurich, where Einstein studied, and then, a FUSE Fellow at the University College in London and then moved over to New York City to be the Asimov Fellow at the American Museum of Natural History.
After this, she moved to Macquarie University in Australia and shortly thereafter she became an Australian Research Council Future Fellow and Orsola’s research focuses on the life and death struggles between stars in multiple star systems.
Orsola is also a great populariser of science. Her commitment to both original research and effective outreach is legendary, and she’s been the Einstein lecturer for the Australian Institute of Physics, which will come as no surprise when you later hear about how Einstein inspired her from a very young age. …
And by the way, her Einstein lecture is fantastic and can be found on YouTube at tinyurl DOT com /orsola18. That’s O -R -S -O -L -A -18, all lowercase … the number 18.
And up until recently, Orsola was also the director of Macquarie University’s Association for Astronomy, including Macquarie’s Observatory and Planetarium and their Astronomy Open Nights, jointly welcoming over 3 ,000 visitors each year.
And right now, Professor De Marco is down here in Melbourne as an invited speaker at this amazing TVU conference. And we’ve got hundreds of presenters and participants from all over the world bringing together the very latest discoveries in this sensational science of transient astronomy.
Thanks for speaking with us today Orsala.
Orsola: You’re very welcome.
Brendan: So, first up, thank you. Before we talk about your current research and the TDU conference, can you tell us about growing up in beautiful Bologna, please? Oh, wow! And could you tell us about those physics experiments you did on a train as a four -year -old and how you first became interested in science and space and all this stuff?
Orsola: So I’m Italian. I grew up in Bologna for the majority of my childhood. And as you can imagine, you know, this is a place full of history, full of astronomy, Bologna and Padua.
Actually, my father lived in Padua and my mother in Bologna. So I grew up between the two cities. both of which had, you know, Galileo teaching at those universities. And so it was kind of in my DNA.
That said, my parents were not scientists. And so that is not where my passion came from. I think there’s some kids just are like that, right? They just are curious about how things work.
And talking of those experiments on the train, I used to drive my mother insane because what I was interested in … is if the train is moving and I am jumping in the train, do I get left behind?
So what I would do, I would take cigarette butts which are common in that time and I would put it in the spot where I was and I was jumping up and waiting to see whether when I came down I would be coming down behind it … right? … as the train should have moved under me. Of course as Galileo had himself experimented with a very long time ago, this is not the way it happens.
If you are moving with the train, you are moving already. When you jump, even if you’re in the air, you preserve the motion that you have when you’re actually on the ground in the train, and you go with the train. So when you come down, you come down exactly at the same relative spot in the train. So I would be jumping down back on the cigarette butt. You know, the nature of my experimental self, which started there and ended there
Today I’m a theorist, I don’t do experiments anymore.
Brendan: Well, tell us a little bit about those school days.
Orsola: Um, like many kids like me, and if you go around this conference, I’m sure the story will be repeated over and over and over. I was a little weird. I was, you know, bullied not severely, but, you know, I was the odd one out. I was not very popular. with the other kids and so I spent my school years in relative isolation .;..some schools being better than others … you know my primary school was terrible my middle school was great and my high school was horrible … and that took me to actually needing to change school because things had gone really bad and that’s actually when I left Bologna for the next … sort of the next chapter in my life
Brendan: Well let’s have a look at that. Let’s summarise it briefly. After school you moved from Bologna University to teach sailing in Scotland then you went down to UCL London where you were awarded your first bachelor’s science degree with first to class honours and topped your year at UCL London.
You stayed on at UCL London. then you flew over to EDH Zurich for a research fellowship, then over to the States for a while for another research fellowship at the American Museum of Natural History.
You also did a lot of outreach, possibly a bit like this, but on a bigger scale, I imagine, then that big move down here to the Southern Hemisphere … and now, now years later you’re still here. But could you give us the why and how you arranged that move from London to New York?
This is for our early career astronomers who are now listening. And do you want to mention that early passion for sailing?
Orsola: Yes … so sailing’s been in my blood. Actually this did come from my parents. My father was a big sailo and I sailed and was around boats and boatyards all my life.
So when I finished high school … so I did high school the last two years in the United World College of Geographic, so that was not in Bologna, was an international school, was in English, was boarding, so very, very, very different. And then I returned home.
I thought maybe I should do university in Bologna, but after three months, I just hated it. I found all those bullying and horrible things. It took me three months. Italy’s wonderful but sometimes it can be horrible and I just left again and I went to London.
But I was kind of early on the start of the next year. I had to kind of take six months off so I decided to teach sailing and I decided in my infinite wisdom to do it in the best country for sailing in the whole wide world and that is Scotland….Not!
It’s freaking cold. The wind is howling the whole time. It was just hard. but it really, it was a formative period of time, let’s say it that way.
So I conquered my fears and my difficulties and I had a really actually good time in the end. And after that, I went back to London. Now, being a sailor remains with me.
I own a boat, it’s my second boat. I bought my first boat about three weeks before giving birth to my first child. It was extremely pregnant and people couldn’t believe it. that I would just buy my first sailboat.
At that time my husband was wondering why doesn’t she like ice cream with anchovies instead of wanting a sailboat. But it turns out it’s been a wonderful experience to have a boat and kids and kids on boats.
And I have bought my second boat here in Australia. I am a sailor. I invite all my friends.
It’s fantastic. I love it!
Brendan: Here you go, you’re out on the boat on the harbour. or you go out in the ocean?
Orsola: Both. Mostly in … actually it’s not in the Sydney Harbour. Beautiful … it is in the next harbour up called Pittwater. And we have a great time. And actually the reason is not just having a great time.
It’s also that when you sail, it’s very self -sufficient. You’re very, at one with nature in the sense that, you know, you’re using the wind for propulsion.
The water is amazing … it’s a commodity as everybody should know … and so there’s a lot of understanding that you don’t own it.
It owns you and you should have respect.
Brendan: Thanks Orsola. So the plan for today is to mainly focus on the science and we’re going to have a quick look at your PhD then we’ll hear about your latest discoveries and your current research and going back the title of your thesis paper is “Cool Wolf-Rayet central stars and their planetary nebulae” … now I also think Wolf-Rayet stars are pretty cool but to keep in sweet withour new listeners can you give us a skinny on what Wolf-Rayet stars are and what is a planetary nebula please?
Orsola: Wolf-Rayet stars Okay … so here we go. So Wolf-Rayet stars are mostly associated with massive stars … massive means more than 10 times the mass of the Sun. They tend to have very powerful winds and these winds generate the conditions to have emission lines.
So these are just like bright bits of radiation in one wave. Now what I did my PhD thesis on. is actually a different type of star. They look identical to the observer but it was realized that not massive at all.
They’re actually very much a solar mass star so they’re usually 10 to 20 times lighter than the massive counterparts that are the famous ones. And they are central stars of planetary nebulae because the way they evolved is so they’re basically the sun, right?
The sun when it gets older than it is today. It blows, it inflates, it becomes larger, eventually loses a lot of mass and the bit in the middle remains a star and the bit has been lost becomes a nebula and we call that the planetary nebula.
The bit in the middle continues to live on and change and sometimes it develops the characteristic of a Wolf-Rayet star and that’s usually when there is no hydrogen left in the star at all, which is a bit odd in itself because kind of everything is hydrogen, right?
Stars .. the universe, everything. So these stars somehow have managed to lose their hydrogen and when they do they develop the characteristics that allow the specific ‘look’ to emerge to the observer.
Brendan: Fantastic, thank you Wolf-Rayet 101. Okay, let’s let’s follow up a bit on that thesis paper for our undergrad and PhD candidates listening.
If you need to have some inspiration for your acknowledgement section in your thesis, your dissertation, have a look at Orsola’s thesis on the UCL website.
I loved it. I think your acknowledgement section at the very beginning of your thesis is so cool. It encourages you to keep on reading and to stay engaged.
It’s very entertaining in itself … before you get stuck into the science. But back to the thesis, I see that you’ve used spectrograph data from the Anglo-Australian telescope, the William Herschel telescope, and the Isaac Newton telescope, and Hubble, of course.
But I know we’re not allowed to have favourites just like our children … but can you tell us if you have a suite of favourite instruments now that are doing the heavy lifting for you and the most productive data gathering for you right now?
Orsola: It’s very interesting that you just dug up that acknowledgement. I didn’t even remember. I had to go back to my thesis and read it. “Oh, yes, I remember” … So I used a lot of observations during my PhD. That is true. The Anglo -Australian Observatory Echelle Spectrograph was amazing … amazingly, I’d never been to Australia. I never took those observations. They came to me via my supervisors and Echelle was built at UCL where I was doing my PhD for the Anglo -Australian Telescope.
As it was known at the time, today is known as the the Australian Astronomical Telescope because the UK pulled out many years ago. I guess that was a premonition of times to come, I would have eventually come to Australia but I had not been there observing myself.
Today I’m mostly a theorist so I use computers more than I use telescopes but of course observations are very close to my heart as I recognize that I do believe observation and theory do not work closely enough at this time.
So I think that because I like transients, this is the topic of this conference, I like things that change. I think that in the end the Rubin Observatory will be playing a massive role … it’s not online yet. And anything that gives me light versus time, we call it light curve, is really something that I am going to look at.
Brendan: Thanks,Orsola. OK, let’s talk now about one of the iconic telescopes that’s producing a lot of great research right now, the James Webb Space Telescope.
I found there are 2 ,000 or 3 ,000 papers referencing the JWST on the ArXiv server. And we’ve got the early release images coming down.
And one of your recent Nature Astronomy papers is coming up. “The messy death of a multiple star system and the resulting planetary nebula as observed by the JWST.”
Now what understandings have come about about NGC 3132 from the JWST images that you studied and what else can we expect from the JWST?
Orsola: JWST? Okay … so it’s a very interesting story how that paper came about. The two characteristics JWST has which are really important and amazing for us are one that it sees in the mid –infrared … so it can see radiation from very cool things.
And the second one is it is just bloody detailed. It’s just so deep and so precise.
And these two things together made that paper. But the interesting thing in the story is how we came up with that paper, that idea, that discovery.
Our discovery was literally on the day when the press release came out and JWST people were all showing these first five images. One of them was of the planetary nebula …what I was talking about before, this kind of the ejected gas of solar-like stars.
And we were looking live, it was evening in Australia, and I see something so strange.
So this object was known before JWST had taken pictures. it was known to be a visual binary, so you see the two stars, where the central star of the planetary nebula is a super faint hot white star, super faint. In previous images, it’s a tiny little thing. The other guy is a star quite bright right next to it. Now, what was interesting in that picture that was being presented for the first time to the world was that the faint guy was super bright and very red.
… and we thought what? First of all super was super faint and super bright and also it’s a hot star they’re not red they’re usually very very blue why was it red?
It had to have dust around it had to have a shroud a cool goopy dust around this very hot star so I literally emailed two or three colleagues and I said “What is going on this thing’s got a dust mist … it must have a dust disk or some dust around it … Let’s take a quick look.”
And so we, we did a round of calls with each other and then we thought, we should … I don’t know, issue a little press release. But in Astronomy, that’s not all you do.
You don’t do press releases, this is embodied just because you saw something on the tele. So we decided to do a very small paper, the data’s public. Let’s analyze what this dust looks like. So we started a little paper with maybe… five, six people.
Within two weeks, there were 69-70 authors in this production. We went from writing a Monthly Notices paper to a Nature Astronomy paper.
We found a lot more. Of course, the detail and nature of the JWST showed us all these bizarre rings around the object that had not quite been obvious before. And so ultimately we did the hallmark and this is quite common I must say in planetary nebula of the complexity that can only be achieved with one companion around the main star if not more.
And in that case there’s definitely evidence that there’s been a binary interactions that means very close companions in addition to wider binaries so there has to be at least three objects plus the one that we see in the JWST picture … which is the visual companion … so that’s at least four.
And then we come up with a fifth. If something is the case, then it has to be also another one. So then became the interesting death. Of course,
Planetary Nebulae are the death trials of solar-like stars or the messy death of a solar-like object. Thanks to the action of all these other stars on the main star.
And that generated the paper.
Brendan: Fantastic, so that image that the public saw, did you and your teams dig into that myriad data and use the different wavelengths and tease it out and pull it apart to find all that classic detail for your paper?
Orsola: Yes, so we truly took everything that was available and pulled it apart. in the sense, for example, with the dust, it’s not enough to say, “Oh, look, it’s reds therefore the dust.” There’s lots of data, different wavebands, and that difference between the different wavebands tells you the temperature of the dust, for example, which indirectly, given, you know, the temperature of the star around which the dust is … tells you where the dust is. So it tells you, for example, the size of the disk. So there’s lots of information that you glean from having more than one picture right? So from having lots of data … when your spectra is even better in this case … there wasn’t yet anything but just having MIRI and the other instrument (I forget the name) and their bands was very very influential to the discovery.
Brendan: Ah thank you …. okay right now might be a good time to have a look at one of your ARC projects. You’re working on that. And it looks like you’ve mentioned dust just before.
It looks like including dust in the models that predict the behaviour, cataclysmic explosions when various types of stars collide.
Now, we know that we’re made of stardust. Thank you, Carl Sagan. Every atom in our body is Stardust created in stellar explosions.
Could you tell us a bit about the dust that you want to include in your models? The title of your project begins … this is the ARC project … “Dusty Models of Stellar Outburst.”
Now, who’s in your team? What are you doing in this project? It’s right there in the title, but can you give us a bit of detail about the methodology that you’re going to use and basically, how’s it going?
Orsola: It’s a wonderful question. So first of all, I think we should tell me what the ARC is.
So the Australian Research Council awards money … It’s not a lot of money. It’s like a project -based money … For ideas or for single projects. So you propose at some point in the year, if you’re happy with it, they give you the money and then usually you can hire one person to carry the brunt of the project with you as in the lead CA being the Chief Advisor.
So the team at the moment as myself and the person who’s a postdoc, his name is Luis Bermudez, is unfortunately not here at this conference and I will be talking about some of the results he’s produced. The other two people people are a researcher from the Free University of Brussels in Belgium…
to be continued
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