Spectroscopy in Utrecht: A Brief History

In the first half of the 20th century, Leonard Ornstein turned the Physics Laboratory of Utrecht University into a center for testing the nascent quantum mechanics through accurate measurements of line intensities in flame spectra. The microphotometer of instrument builder Willem Moll was the key to this success. Marcel Minneart used this instrument to study stellar spectra at the Utrecht Astronomical Institute, and in particular for the Photometric Atlas of the Solar Spectrum. When the opportunity came in the 1960s to build instruments for research from space, it was natural that Kees de Jager opted for spectroscopy, in X-ray observations of the Sun. The expertise developed in this program allowed the Space Research Organisation of the Netherlands to be a principal player in the development of X-ray spectrographs on the Einstein, EXOSAT, Chandra and XMM-Newton satellites.