Adriaan Blaauw

OB Associations and the Fossil Record of Star Formation

Properties of OB Associations within 1.5 kpc are reviewed as “fossils” of local star formation, and as a reference frame for the more detailed discussions, elsewhere in this volume, of star formation occurring within the sample. Special attention is paid to the process of sequential star formation. For the nearest associations this can be traced back to the formation of the Gould Belt between 30 and 50 million years ago. A few remarks on future research conclude the review.

The Calibration of Luminosity Criteria

Attention is drawn to important systematic effects in the calibration procedure due to the accidental errors in the measured luminosity criteria. The present state of the luminosity calibrations in the MK system is reviewed with reference to recent work based on proper motions and radial velocities, and on trigonometric parallaxes, resulting in evidence for corrections of about — 0.4 mag. for the K0–K5, III stars. Brief reference is made to the developments with regard to the M v (K) system.

Jan Hendrik Oort (1900-1992)

With the death of Jan Hendrik Oort on 1992 November 5, at the age of 92 years, the astronomical community lost one of its most distinguished members. In a span of seventy years of creative activity, Oort witnessed, and contribued to, the development of our picture of the cosmos from one limited to ill defined borders of our Galaxy, to the remote depths of the universe. He shared his intellectual gifts, his inspiration and his enthusiasm for the science of his choice with numerous colleagues, young and old all over the world. For many of them, his passing away means a loss of a dear and highly respected friend. Oort was the Cathern Wolfe Bruce medallist of the Astronomical Society of the Pacific in 1942, now a half century ago!.

STAR FORMATION IN THE ORION ARM

We assemble principal constituents of the morphology of the Orion Arm within 1500 pc as a starting point for the study of progression of star formation.

Meeting Kapteyn in the Kapteyn Room

In the early 1970’s the Kapteyn Laboratory moved from the building Broerstraat 7, next to the University Headquarters where it had been since the years of Kapteyn, to the campus now known as the Zernike Complex. In planning this move, the Board of the University fulfilled the astronomers’ wish to establish in the new quarters a Kapteyn Room dedicated to the founder of the institute. After having been housed on the Zernike Complex for about a decade in the building now known as the “Hoogbouw”, astronomy obtained its current accommodation including the Kapteyn Room in the Zernike Building. The room was furnished with items left from Kapteyn’s days, and serves to store the collection of notebooks, tables, etc. used by Kapteyn and his first successors. Let us dwell for a moment in this room and survey its contents.

Stellar evolution and the population concept after 1950; The Vatican Conference

In the development of the concept of stellar populations the classification scheme adopted at the Vatican Conference of 1957 represents a major milestone. Thirteen years after Walter Baade’s seminal papers, the conference reviewed progress in relevant fields of research and formulated a classification of population types that would remain the principal reference for the next decades. I shall review developments preceding the Conference, the initiatives that led to the Conference, the new scheme, and a few developments of later date.