Asteroseismology Shakes Up Theory of Stellar Evolution

Asteroseismologists are thus able to derive key parameters such as the size, mass and density of the star, and how long it will be able to sustain the nuclear fusion processes at its core. The speed at which the star’s core rotates is relevant in this respect. It affects the homogeneity of the material inside, and thus the efficiency of its nuclear fusion processes. “If more matter is mixed in the core, the star can live longer,” Aerts explains.

And this is one area where the accepted theory of how stars live fell flat. Analysis of the data revealed that the cores of ageing sun-like stars don’t spin nearly as fast as scientists had assumed. “What we had in the theory was totally wrong,” Aerts comments.

“We found that the core rotation was a factor 100 slower than the theory predicted,” she notes. This finding has implications for many areas of astrophysics, and consequently attracted particular attention.

Along with this unexpected insight, PROSPERITY delivered several other advances. It created new information about tidal forces on binary stars, for example, i.e. stars that orbit around the same central point as a second star. It also built a new instrument for ground-based observations.

As a further important contribution, the project enabled Aerts to involve and train a number of fledgling researchers, several of whom have now embarked on promising international careers. About a dozen young astronomers were thus given an opportunity to reach for the stars.

Aerts is excited that PROSPERITY has rocked assumptions. “The purpose was to test the theory. And luckily the outcome was that the theory was not good,” she comments. “Imagine if we had confirmed the theory – that would have been boring, right?”

Her groundbreaking work in the project won her a prestigious award in 2012: the Francqui prize, also known as the Belgian Nobel Prize. Aerts is the first – and as of 2016 still the only – woman to have received this distinction in the exact sciences, and she doesn’t intend to rest on her laurels.

She is also the first of only two researchers so far to have obtained two successive ERC Advanced Grants in astronomy. A new project is thus already under way, again with support from the ERC. The current endeavour focuses on modelling the seismic processes of massive stars.

It’s known as MAMSIE, an acronym that the full project title was constructed to support – with excellent reason. “That’s the nickname that my kids have given me,” Aerts reveals.