asteroseismology

Asteroseismology is the study of oscillations in stars. By measuring the frequencies and patterns of stellar pulsations, it reveals the internal structure, dynamics, and evolution of stars that are otherwise inaccessible. Oscillations arise from various driving mechanisms, including stochastic excitation by convection in solar-like stars and opacity-driven pulsations in more massive variables. The observed frequencies depend on a star’s mass, age, rotation, and chemical composition, making pulsations a powerful diagnostic of stellar interiors.

Oscillations are commonly classified as p-modes, g-modes, or mixed modes. Pressure modes are acoustic waves that probe the outer layers and have higher frequencies; gravity modes are buoyancy-driven and probe deep interiors with lower frequencies. In evolved stars, mixed modes couple p- and g-mode cavities, allowing access to core properties and internal rotation. Classic instability strips host opacity-driven pulsations, including delta Scuti, beta Cephei, and rapidly oscillating Ap stars.

Observationally, asteroseismology relies on precise time series of light or radial velocity. Space missions such as CoRoT, Kepler, and TESS provide long, stable photometric data, while ground-based networks measure Doppler shifts. Frequencies are analyzed via large and small frequency separations and by identifying mode degrees. Inversion techniques and forward modeling translate frequency patterns into internal profiles of sound speed, density, and rotation.

The resulting constraints yield fundamental parameters such as mass, radius, and age, and reveal internal rotation profiles and the extent of convective zones. Asteroseismology enhances stellar modeling, exoplanet host characterization, and, more broadly, studies of stellar populations and Galactic evolution.

Challenges include surface-effect corrections, mode identification, and model dependencies. Ongoing observational campaigns and theoretical advances continue to improve precision and expand the range of stars accessible to asteroseismic analysis.