The heartbeat of the stars

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RAS public lecture, 8th April 2014

by Prof. Yvonne Elsworth, University of Birmingham

Our knowledge of how stars change and evolve underpins our understanding of both the far reaches of the Universe and nearby stars including our Sun. In recent years these studies have all been revolutionised by observations of the interiors of stars. The methods are inherently simple even if they require precise techniques to make them effective. The physics that underpins the method is purely classical. It has been discovered that, for certain kinds of stars, the turbulent conditions that prevail in their outer convective regions cause sound waves to propagate and resonate within their interiors. This leads to small, periodic changes in the surface properties that can be observed. This field is known as asteroseismology. For the Sun, we are able to build seismic maps of the interior and hence make visible the conditions in different regions including the energy-generating core. Several major deductions which had far-reaching implications are discussed in the lecture.

For stars more distant than the Sun, the information obtained is more limited. However, the recent data from the Kepler satellite has enormously broadened the field because we are no longer restricted to one sample (the Sun at its current age) from the wide range of states that the Sun and stars of roughly similar mass will experience in their lives. This lecture gives examples of how asteroseismology has impacted the study of planets in the habitable zones of their stars and also how we are able to probe conditions in the centres of evolved stars.