The ins and outs of red-giant stars using asteroseismology
01 / 2011 - 01 / 2014
The aim of this project is to perform an observational study of both oscillations and surface structures (granulation) and their interactions in red-giant stars. These phenomena are driven by turbulent motions in the outer layers of red giants and can provide vital information on the internal structures and constraints on the poorly understood mechanism of mass loss in AGB stars. Long time series of high-precision photometric observations from the CoRoT mission and NASA Kepler satellite, which are currently taking data, will be used in this study. Stars are the building blocks of galaxies, and are crucial sources of energy for the conditions necessary to support life. Knowledge of how stars are born, evolve and die underpins our understanding of the Universe. Observations have shown that a majority of stars show some form of periodic variations. These variations are an invaluable tool to peer deep inside stars to gain an understanding of their inner structure. Stars cooler than the Sun, such as red giants, have turbulent outer atmospheres. In these atmospheres the turbulent convection stochastically excites oscillations. From these oscillations we can measure, among others, the masses and radii of the stars. Furthermore, convection currents that transfer heat from below to the stellar surface are visible on the surface. The rising gas columns, surface flows and the location where the gas sinks are visible as separated areas or granulation cells. These cells provide information on the extent of the outer convective zone and possibly on its turbulence. Both oscillations and granulation originate in similar regions in the star, while they have different typical timescales and can both be observed in long time series of photometric data. Thanks to the recent launch of CoRoT and Kepler this study of both oscillations and granulation will now be possible for the first time.
Sterren worden geboren en ontwikkelen zich De zon is een volwassen ster, maar zal over een paar biljoen jaar sterk veranderen en een oude ster worden Het doel van dit onderzoeksproject is de interne structuur van oude sterren te achterhalen.