Obituary for Professor Maarten Schmidt

October 12, 2022

A few weeks ago, Professor Maarten Schmidt, an external scientific member of the MPE for many years and involved in numerous projects, passed away. The two former MPE directors, Joachim Trümper and Günter Hasinger, who worked with Schmidt for many years, remember.

On the 17th of September 2022, Maarten Schmidt passed away in Fresno, California, at the age of 92. As a student of Jan Oort, he received his Doctor of Philosophy from Leiden University in 1956 with a thesis on the structure of galactic matter distribution based on optical and radio observations. He was already known for his thoroughness and persistence when he made his most famous discovery in 1963: measuring the redshift of the optical spectrum of the quasi-stellar radio source (quasar) 3C273, which is z = 0.158, showing that the object is at a cosmological distance (~ 500 Mpc) and has an extremely large luminosity. His further work was essentially devoted to the study of quasars, which are mass-accreting supermassive black holes. Maarten Schmidt has received many honours and awards, including the Helen B. Warner Prize in 1964, the Schwarzschild Medal of the Astronomical Society in 1968, the Gold Medal of the Royal Astronomical Society in 1980 , the James Craig Watson Medal in 1991, the Bruce Medal in 1992 and the Kavli Prize for Astrophysics in 2008. Furthermore, he has been a member of numerous academies.

It was a stroke of luck for MPE that in 1984, I (J.T.) was able to recruit Maarten Schmidt to collaborate on the ROSAT project together with Riccardo Giacconi, who had discovered the diffuse and isotropic X-ray background in 1962. Our goal was to investigate the composition of this very background radiation with the help of deep surveys of the sky. The many meetings at MPE before and after the start of ROSAT (1990), which served to plan the observations and discuss the data obtained, and which often ended in the evening at the historic Augustinerbräu in Kaufinger Strasse with pork knuckles, dumplings and beer, remain unforgettable for all those involved.

Maarten was responsible for the follow-up optical observations of the X-ray sources, first with the 5-metre Hale telescope on Mount Palomar and later with the 10-metre Keck telescopes in Hawaii, which showed that the sources of X-ray background radiation were essentially distant Active Galaxies. During these observing campaigns he introduced me (G.H.) to the secrets of optical spectroscopy.

With ROSAT we had already resolved about 80% of the X-ray background radiation into discrete objects. After the end of the ROSAT mission in 1998, the measurements were continued almost seamlessly from 1999 with Chandra and XMM-Newton until 2005. In the process, we were able to resolve about 95% of the background into sources.

Since 1993 Maarten Schmidt was an external scientific member of MPE. Those who had closer contact with him enjoyed his friendship, wit and humour. Unforgotten are the invitations to his home in Pasadena, where his wife Corrie took care of the guests' well-being and Maarten - equipped with binoculars – observed various comets or waited for the International Space Station to appear in the sky. He had been married to Corrie for 65 years when she died in 2020.

We will not forget Maarten. Our sympathy goes to his daughters Anne, Elizabeth and Marijke and their families.

Joachim Trümper                          Günther Hasinger 

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