Astronomer works to find universe’s missing puzzle pieces

Growing up in Antananarivo, Madagascar, Sambatriniaina Rajohnson loved watching films depicting real or imaginary science and technology stories. Science fiction portraying space and life on other planets, later on, inspired her to study astrophysics at the University of Antananarivo.

Her fascination with space earned Rajohnson a L’Oréal-UNESCO Women in Science Young Talents Sub-Saharan Africa Award at the end of 2024. She was recognised for her research revealing how unexplored galaxies impact the universe. A total of 29 scientists were honoured for their work.

According to Rajohnson, she would be thrilled if science could revolutionise travel on Earth and enhance people’s capabilities for space exploration.

The astronomer, who believes that science has no gender and is “all about advancing knowledge and pushing boundaries”, spoke to University World News about her work and her determination to overcome a lack of access to resources, including equipment and the internet.

She also shared her insights into how South Africa’s MeerKAT radio telescope has been contributing to finding a missing piece of the puzzle about the universe that astronomers have been grappling with.

UWN: Tell us about your childhood and dreams back then.

SR: I grew up in Antananarivo, Madagascar, as an only child. Like many kids, I was fascinated by airplanes. Seeing them fly across the sky, I would often exclaim: “Woah, that’s a plane!” One of my dreams, since then, was to experience flying in an airplane, and I am happy it came true.

From a young age, I also loved documentaries, science fiction, and adventure movies such as Indiana Jones in which discoveries of aliens living on new planets or ancient relics were made. This sparked my curiosity and questions in my mind.

I dreamed of becoming either an aircraft pilot or a passionate scientific researcher working in a lab – although I had not yet decided on a specific field.

I attended private primary and secondary schools, called Mahasoazaza, and, later, went to a public high school, Lycée Jules Ferry Faravohitra, where I earned my scientific baccalaureate in 2012. I then pursued physics at the University of Antananarivo, completing my bachelor degree in 2015 and my masters degree in astrophysics in 2018. Most recently, I completed my PhD in astronomy at the University of Cape Town in South Africa.

UWN: When did you develop an interest in astrophysics?

SR: My interest in astrophysics was sparked during my university years. As a child, I did not know that pursuing astronomy was even possible in my country, so I tried to keep my dreams realistic at the time. My fascination with the sky was always there, but my career path felt uncertain.

Everything changed during my second year of undergraduate studies when I learned that an astrophysics curriculum had been introduced at the university. That moment felt like a turning point for me – almost like a sign that this was the direction I was meant to follow. I did not hesitate; I seized the opportunity and fully committed to pursuing astrophysics when it became available.

UWN: Tell us about your research and its importance?

SR: Our galaxy, the Milky Way (a huge collection of stars, dust and gas), appears as a glowing band of stars in the night sky.

However, the dense stars and dust in our galaxy block the view of what lies beyond. While visible light is completely obstructed, even infrared light struggles to penetrate these regions. This creates the Zone of Avoidance (ZoA), a large, unexplored region of the sky and a gap in the maps of our universe.

Dense concentrations of matter exert a gravitational pull on their surroundings. It has been observed that our Milky Way moves at an incredible speed of over two million kilometres an hour, pulled by massive structures in space, which seem to lie within the ZoA. One key candidate that could possibly contribute to this motion is the Vela Supercluster, a huge collection of galaxies partly hidden in the ZoA.

Using the MeerKAT radio telescope located in the Karoo desert, in South Africa, I am working to map and uncover the obscured galaxies in this region.

By detecting galaxies out at a distance of 1.1 billion light years, I aim to fill this gap and quantify their possible contribution to our galaxy’s motion. Radio waves are essential for this work, as they are the only tool capable of penetrating the Milky Way’s dust, providing a clearer view of what lies beyond.

UWN: What do you hope to achieve with this mission and why is it important?

SR: By mapping the hidden galaxies in the Zone of Avoidance, particularly the Vela Supercluster, I aim to determine how much mass it contains and its possible role in pulling the Milky Way. This could help understand a missing puzzle about the observed motions of the universe that astronomers have been trying to solve for years.

UWN: What are galaxies, how many have you discovered, and how did you discover them?

SR: Let’s think of galaxies as vast systems with ingredients like stars, hydrogen gas, dust, and invisible dark matter, all held together by the ‘pot’ of gravity.

Using the MeerKAT radio telescope, we have discovered over 1,500 galaxies in a heavily obscured region of the sky – about 10 times more than previous surveys in the same area.

To find these galaxies, MeerKAT is pointed at the region of interest, and we search for signal peaks rising above the noise. These signals represent neutral hydrogen emissions from galaxies. In 2D (two-dimensional, a description of shapes that can be defined as a flat figure or a shape that has two dimensions – length and width), this signal appears as a small, bright dot standing out against the background noise.

UWN: Lastly, what challenges have you faced as a woman scientist, and what needs to be done to support the next generation of female scientists?

SR: In our first-year undergraduate class, we were only around 20 women compared to hundreds of men. That might be demotivating for some, but it did not destabilise me at all.

I can say that I have been fortunate not to face gender-specific challenges, thanks to the supportive environment around me. However, cultural and gender stereotypes still exist, and mentorship and family support are vital to overcome them.

The main challenge I faced was limited resources during my studies. For example, I only got my first laptop during the first year of my masters programme.

This is where programmes such as L’Oreal for Women in Science play an important role – not only in addressing resource limitations, but also in fostering a powerful network among women scientists, empowering them to support one another. More such opportunities should be introduced earlier in women’s careers, not just at the PhD level.