"Literally, it feels like I'm living my dream," Stephanie Buttigieg says as her face lights up.

Buttigieg, 24, from Lija, holds a Bachelor's degree in Mathematics and Physics from the University of Malta and a Master's in Astrophysics from the University of Cambridge. She has been in Cambridge for two-and-a-half years and is expected to complete her PhD in September 2027.

In an online interview with this media house, she said she always wanted to further her studies abroad. She applied for Cambridge after completing her Bachelor's degree in Malta.

"All of a sudden, it went from being a dream to being a reality," Buttigieg said. "It's just been amazing. I love Malta, it's my home country, so I do really miss it and my culture, but Cambridge is such a leading institution. The research that goes on here is really at the forefront of scientific discovery."

Buttigieg said she was always captivated by mathematics, so much that she would go back to studying maths as a "break" from studying other subjects during her O-Level studies. "I was always fascinated with how things follow logically and how there was one clear answer. It felt like a puzzle to me."

As she went along with her studies, she became more aware of Space. She recalled having the choice to either go into computing and do programming, or go further into maths and physics. She eventually decided to continue doing what she always enjoyed doing and learning new maths techniques, which ultimately led her to astronomy modules.

She said that she remembers finding the field of cosmology first, which she described as understanding the evolution of the universe. She remembers falling in love with the different phenomena and theories in this field, and realising that there is so much of the universe that humanity still does not understand.

"I always loved learning, and the moment I realised that the universe is so vast, that there are so many things that we don't understand about it... that gave me the opportunity to always learn more and more. I was hooked from there."

Black hole mergers

Buttigieg's PhD research is focusing on supermassive black hole mergers. Asked what led her to choose this subject, she replied that during her undergraduate and master's programmes, she did different research related to theories of gravity. She continued that there is great difficulty in being chosen and funded for a PhD position, and that there was no one working on the kind of research she had done in the past at Cambridge's Institute of Astronomy, and so she had to delve into a new field. She mentioned that making such a sudden change after spending years building experience can be frightening, but talking to several different supervisors helped her explore various options.

"So, the summer before signing my PhD, there was a big announcement of the detection of the gravitational wave background. I found out that it's most probably these supermassive black holes which are at the hearts of galaxies and merge with each other eventually. They give off gravitational waves.... And you detect a background, so a continuation, like a hum across our galaxy sourced by these kinds of supermassive black hole mergers."

Buttigieg said that she remembers being mind-blown at this revelation, and that she realised that this is what she wanted to focus her studies on.

The newsroom asked Buttigieg about some of the most intriguing discoveries or insights she has had while studying this field.

She replied that she had recently submitted a paper for peer review, and so the findings are quite fresh. She continued that the field uses cosmological simulations, which she said are simulations run on high performance supercomputers which essentially mimic a small portion of the universe and have different particles representing stars, dark matter, gas and black holes. She went on to explain that while researchers follow the movements and dynamics of these particles, it's impossible to simulate the universe to exact precision as doing so would require infinite computing power.

The simulations make use of some assumptions, one of them being "limited resolution", which she said means that individual objects can be tracked when they are far apart from each other, but that they can no longer be tracked when they approach a certain distance which leads to them "blending together". She remarked that this is a known issue, and that people have worked on explaining what happens when two black holes merge in this situation.

Predictions

She found that even above the resolution limit, meaning even when two black holes are still separate, there are still some issues in the code that researchers need to be careful of. She said that some black holes are merging "prematurely". She commented that researchers need to make sure that this is accounted for in order to make good predictions for future gravitational wave observations.

Buttigieg was asked what the exact differences are between black holes and supermassive black holes, as well as how they form.

She said that black holes come in "two main flavours" for astronomers, one being stellar mass black holes, the lighter ones which are about the mass of our solar system's sun, and the other type being supermassive black holes "which are about a million to a billion or even 10 billion times the mass of our sun".

She said that the way stellar mass black holes form is understood to be from when a large enough star runs out of fuel, it collapses in on itself and forms what is known as a singularity, which she described as a "really dense region in spacetime". She continued that this singularity is surrounded by an event horizon which nothing can escape from, and commented that this is what is referred to as a stellar mass black hole. She added that mergers of these types of black holes have been detected using gravitational waves.

In regard to supermassive black holes, Buttigieg said that they are different from stellar mass black holes because they reside at the hearts of galaxies. "You can think of each galaxy having one of these really, really giant black holes at the centre," she commented.

The question of where these supermassive black holes come from is an open research question, she remarked, as it is still not quite understood how they form.

Science and communication

Buttigieg is the co-chair of the Women's Network at the Institute of Astronomy at Cambridge, and describes herself as being deeply passionate about science communication and making astronomy accessible to the general public as well as increasing the representation of women in science.

She said that there are quite a lot of gender stereotypes still around in society, and that while a lot of progress has been made, "there's still this kind of messaging that goes out to young girls sometimes, that they're not quite as good at science as boys are... a lot of the times these messages are quite subtle rather than in your face". She added that she believes this subtle message, which girls begin to internalize from a young age, may discourage them from pursuing science.

"Obviously not everyone gets discouraged, but some people might, and that's where I think representation becomes super important. There are women scientists, there are Maltese women scientists as well, and I think it's quite important to share that so that if a young girl comes across a woman talking about these subjects, there's that click of, oh look, there's someone like me doing this kind of research."

Naming women who have particularly inspired her in the scientific field, she spoke of her supervisor, who she said inspires her on a day-to-day basis and teaches her how to be a better scientist. She also mentioned Professor Dame Jocelyn Bell Burnell, who Buttigieg said was a PhD student in Cambridge and discovered pulsars, of which the discovery was awarded the Nobel Prize, "but not to her, obviously there is an interplay of being a woman and also being a student, so she wasn't credited as she should have been". Buttigieg spoke of how she was able to meet Professor Bell Burnell in 2024, and described her as a real inspiration especially with how important pulsars are for her field of studies.

On the matter of outreach and science communication, Buttigieg said that she is personally very active on social media, adding that she thinks social media is a great platform due to accessibility. She has a series on her social media pages called Astronomija bil-Malti (Astronomy in Maltese), where she speaks about space-related subjects and explains them in Maltese. She remarked that doing this can be quite a challenge for her as she has never studied science in Maltese, "but it's a very fun challenge, and it keeps me connected to my mother tongue, which I miss practising every day".