When Professor Conny Aerts was a child growing up in rural Belgium, she was fascinated by the stars, clearly visible owing to the lack of light pollution. But she wasn’t out there glued to a telescope.
“No, I was out there with my eyes actually!” she says.
“Lying in the grass, because I come from very far out in the countryside. It was pure curiosity, that I already had in primary school. What are the stars? Somehow I turned that into my profession. I just followed my curiosity.”
That curiosity led not only to a PhD in Astrophysics at KU Leuven, where Conny is now a professor, but to the development of a whole new field within the discipline. As a pioneer of Asteroseismology, she explores what oscillations on the surface of the stars can tell us about their internal structure. These “songs of the stars” are, it appears, the key to their mysteries.
“When we talk about songs of the stars, we’re actually describing sound waves created by stars,” she explains.
“A star is a hot gaseous ball that is rotating. If you press the material up and down in a complex way you create sound waves, which travel straight through the star. It allows us to unravel the internal pressure of the gas, its density and temperature, but above all and this is what only Asteroseismology can give us, the internal rotation of the gas, and this is really setting the life of the star.”
These investigations only became possible once recent space technology made the measurement of the sound waves possible.
“The field is fairly young as a subset of Astrophysics, because we needed the measurements of these tiny little vibrations. They actually change the brightness of the star, and we can measure that nowadays with space missions. But we needed that machinery to be operational above the earth’s atmosphere before the field could take off.”
Conny will adjust the frequency of the sound waves to make them audible to the human ear, giving the Darwin audience a taste of the soundscape of the heavens.
“I mainly specialise in stars more massive than the sun, but I will start with the sun first because that’s the star we know best. Stars that are bigger than the sun really rotate fast, and what is new is that the stellar oscillations show us how the gas inside the star is rotating compared with at the surface.”
In the same way as earthquakes reveal the interior of our own planet, these sound waves provide a unique glimpse of the inner workings of stars, which are otherwise unknowable.
“What really matters for stellar life is the rotation in the inner part, and these waves are the only way to get that. So my contribution to this field is really the internal rotation of the stars and the impact it has on the life of the stars, and by implication also on the materials that stars create and that the universe is getting from the stars.”
A century ago, in 1926, Cambridge astronomer Arthur Eddington (who succeeded to the role of Plumian Professor of Astronomy following the death of Sir George Darwin), published his landmark work, The Internal Constitution of the Stars. Exactly 100 years later, Conny Aerts will address one of the major questions he left unanswered.
“The key thing is that sound waves allow you to see the invisible. Eddington wrote that need in his book in 1926, but he had no clue how to solve this question of how we could derive the interiors of stars. And now we know that the songs of the stars are the answer.”
Join us for Conny’s lecture, Songs of the Stars: Unravelling Stellar Music with Asteroseismology, at 5.30pm on Friday 27th February.
