THE SUPERCLUSTER-VOID NETWORK - IV - THE SHAPE AND ORIENTATION OF SUPERCLUSTERS

We present a study of the shape, size, and spatial orientation of supe rclusters of galaxies. Approximating superclusters by triaxial ellipso ids we show that superclusters are flattened, triaxial objects. We fin d that there are no spherical superclusters. The sizes of supercluster s grow with their richness: the median semi-major axis of rich and poo r superclusters (having greater than or equal to 8 and < 8 member clus ters) is 42 and 31 h(-1) Mpc, respectively. Similarly, the median semi -minor axis is 12 and 5 h(-1) Mpc for rich and poor superclusters. The spatial orientation of superclusters, as determined from the axes of ellipsoids, is nearly random. We do not detect any preferable orientat ion of superclusters, neither with respect to the line of sight, nor r elative to some other outstanding feature in the large scale structure , nor with respect to the directions of principal axes of adjacent sup erclusters.