On a Cluster of Nebulae in Hydra

Abstract

Clusters of nebulae are the largest known aggregations of matter which possess definite individual characteristics. In preparation of a theoretical study of the large scale distribution of matter in the universe we propose to analyze some simple structural features of a number of clusters of nebulae. Most of the observational data used were obtained with the 18-inch Schmidt telescope on Palomar Mountain. Photographs taken with this instrument, because of their excellent and uniform definition over a field of about seventy square degrees are well suited for a survey of a number of the more near-by clusters of nebulae. In the present report we shall be concerned with a cluster of nebulae in Hydra. The three nebulae NGC 3285, 3309 and 3312, the apparent magnitudes of which according to the Shapley-Ames catalog are m = 13.2, 12.7 and 13.1, respectively, lie near the line of sight of the center of the cluster (at about R.A. 10h 34m, Decl. -27° 16', epoch 1950). The distribution of the nebulae brighter than about the apparent magnitude m = 16 is shown in figure 1.