Heinrich Johannes Wendker, retired professor at Hamburg University, died on 3 April 2008 at the age of 69 at Reinbek near Hamburg, Germany. He was born on 30 June 1938 in Gimbte, near Munster, Westphalia, Germany. In 1958 he finished high-school and started his studies of mathematics, physics, and astronomy at Munster University. In 1960 Wendker joined the Astronomical Institute at the University and became attracted to the relatively new field of radio astronomy. In the same year he participated in a radio survey (at a wavelength of 11 cm) with the 25-m dish of Stockert observatory. In 1964 he joined the NRAO in Green Bank, Virginia, for one year and started with observations of the Cygnus area of the Galactic plane that would become a real passion for him (resulting in over twenty publications about the Cygnus X region, a deep study of the structure of the local spiral arm). Wendker was awarded the Ph.D. in 1966 (University of Munster), and in the same year he accepted an appointment at the University of Illinois at Urbana. There he participated in the All Sky Survey of the Vermilion Radio Telescope including the Cygnus region. In 1968 he joined the newly founded Max-Planck-Institut fur Radioastronomie at Bonn, Germany, where he got involved in planning the institute's new building among other things. In 1972 Wendker was appointed Professor of Astronomy at Hamburg University where he would spend most of his academic career. From 1985 to 1989 he was director of the observatory (Hamburger Sternwarte), and from 1989 to 1991 he was Dean of the physics department.
Wenker's research activities concentrated on the radio structure of the Milky Way, especially on the Cygnus region, observing the radio continuum emission at different frequencies in order to separate thermal from nonthermal emission (i.e., HII-regions and SNRs). He identified foreground stars and extragalactic sources in the background. Additional observations of molecular lines and of the neutral atomic hydrogen completed these studies. These activities culminated in participation with the Canadian Galactic Plane Survey [CGPS] of the Dominion Radio Astronomy Observatory [DRAO]. With the detection of radio emission from Betelgeuse (a Ori) Wendker opened the field of normal radio stars (e.g., the editorial in Nature 241, 9 (1973)). He detected dozens of radio stars, among them MCW349 and P Cyg. Another highlight was the detection of radio recombination lines in MCW349. Observations of a few dozen radio stars led to the conclusion that many of them possessed atmospheres not known before. Wendker collected and catalogued all radio observations into a catalog of radio stars (1978, 1987, 1995). This data collection of spectra of the radio continuum emission of radio stars contains clues relating to the radiation mechanism responsible for the observed radio emission. Variability of the emission of some stars points at nonthermal radiation.
Together with Alfred Weigert, Wendker published a textbook on astronomy and astrophysics, Astronomie und Astrophysik--ein Grundkurs. For the 4th edition, L. Wisotzki became a co-author. This introductory text is widely used at high-schools and for the first-grade university level in German speaking contries.
Wendker is survived by his wife, Walburga, and two sons, Martin and Andreas. He was a dedicated researcher and academic teacher. Many colleagues will remember his advice and support. We have lost a colleague and a good friend.