Hidden clusters in the southern Milky Way

At visual inspection of objective-prism plates of Milky Way regions one frequently detects pairs or sometimes higher multiples of spectra which are so similar in appearance and so close together that they form a conspicuous configuration for the eye. A statistical analysis shows that the observed occurrence of this phenomenon, down to a certain limiting magnitude and up to a certain value of the angular separation of the components, considerably exceeds the expected one - if it should be considered as produced entirely by random coincidence. Therefore it is reasonable to assume a physical explanation behind this sort of agglomeration. In connection with a large survey of the Southern Milky Way, carried out at the Stockholm and Uppsala observatories, several thousands of such coincidences have been registered. About a hundred of them have been subjected to a special investigation, intended to give an answer to the question about their physical interpretation. Although the methods have been neither very rational, nor always point-to-point reliable, the scrutiny has shown pretty well that an overwhelming majority of the 'candidate' objects do reveal stellar clusterings of various types. (Auth.)