UVES spectrum of the Sun

The image shows part of a test spectrum of the Sun, taken by UVES in the Laboratory in Garching on October 19, 1998. The bright (nearly) horizontal lines correspond to adjacent, small wavelength ranges of the solar spectrum. Within these, many vertical dark lines indicate the presence of certain elements in the solar atmosphere, for instance gaseous hydrogen or iron. From the line shapes and their depths, it is possible to determine the temperature, pressure and chemical abundances of this gas. Small shifts in wavelength of such lines, when measured in other stars, indicate velocity changes due to the Doppler effect that may be caused by invisible planets circling the observed star.