Water on the Sun: the Sun yields more secrets to spectroscopy
Analysis of sunlight, which started the discipline of spectroscopy, has been the key to a number of major scientific discoveries. Sunspots, which are much cooler than most of the Sun's surface, have particularly rich and complicated spectra which has long been thought to be due to very hot water. The challenge of analysing this spectrum has stimulated the development of new theoretical procedures based on full quantum mechanical treatments of the vibrational and rotational motion of the water molecule. The result has been the identification of novel spectral features and a deeper understanding of how excited molecules such as superheated water behave. This work has applications ranging from the models of cool star atmospheres and rocket exhausts to the possible automated detection of forest fires. Perhaps the most interesting result is the insight given to understanding how our own atmosphere absorbs sunlight, and the possible consequences that this may have for modelling the greenhouse effect.