1. The problem statement, all variables and given/known data From near to the center of the solar disc, Fe I line emission from point X shows a spectral line with components 666.823, 666.830 and 666.837 nm, around the rest wavelength of 666.800 nm. The central component is not as bright as those at the longer and shorter wavelengths. Measurements at Y around 12,000 km away from X on the Sun’s surface show three components at 666.826, 666.829 and 666.832. In this case, the central component is brighter than the components at longer and shorter wavelengths. For X and Y determine the velocity of the gas containing the iron relative to the observer. Calculate the magnetic field strength at each point 2. Relevant equations I think the Zeeman effect is involved. 3. The attempt at a solution I don't want to be told the answer. I would like to work it out myself. However, the course notes assume prior knowledge, and I don't know where to start. If I could just be pointed in the right direction, that would be a great help. Thank you.