Star-quakes help reveal content of stars 'hotter and more massive than the Sun'

Researchers from the Institute of Astrophysics of Andalusia (IAA-CSIC) have for the first time, shown the validity of asteroseismology for the study of stars that are hotter and more massive than the Sun.

Juan Carlos Suarez, researcher at the Institute of Astrophysics of Andalusia (IAA-CSIC), said thanks to asteroseismology we know precisely the internal structure, mass, radius, rotation and evolution of solar type stars, but we had never been able to apply this tool efficiently to the study of hotter and more massive stars.

In some sense, stellar seismology conceives of stars as resonating cavities where the movement of gas generates sound waves. Many of these sound waves tend to fade out, but if they find any mechanism to sustain them, they will reach an equilibrium on the surface of the star and deform it, producing different modes of oscillation (which can be observed as changes in temperature and glow).

As they go through different parts of the star, the modes of oscillation are affected and, depending on where they went, will take one form or another on the surface. "Some modes are more sensitive to what is happening inside, others to the size of the nucleus. All of them are influenced by chemical composition, internal structure and age of the star. We use mathematical models to determine what type of structure and characteristics are behind the modes that are observed," explains Juan Carlos Suarez (IAA-CSIC).

The study has centered on a type of star known as Delta Scuti, whose mass ranges between 1.5 and 2.5 times that of the Sun and which rotates so fast that it can be deformed (instead of being spherical it tends to flatten out). Due to its rapid rotation its oscillation spectrum is difficult to interpret, and although regular patterns had been detected earlier, its physical properties were unknown.