A (2). Overall Structure: Space Distribution and Motions in the Disk

Abstract

The population of the disk consists of a great variety of objects with a wide range of concentration towards the galactic plane and of peculiar motions. The extreme population I objects like interstellar gas and dust and super-giant stars, show quite different properties with respect to space distribution and motions, compared to such stars as, for instance, the common G and K giants. The discussions at the conference have concentrated on the observational possibilities of studying the correlation—or the lack of correlation—between the space distributions of different kinds of objects. From recent theoretical as well as observational work it has become apparent that there is a wide range in the ages of the stars contributing to the disk population, from a few million so some 1000 million years. The differences in the distributions of the various kinds of stars very probably must be interpreted in terms of these differences in age and evolution. The most intriguing problem for the present thus seems to be this: Can we trace large-scale structure in the distribution of objects of different ages, and can we derive information on the evolution of the galactic system and of the stars themselves from the degree of resemblance in the large-scale structure exhibited by different objects?