Alignment of distant radio sources

In 1972, earlier workers investigated the relative orientation of 74 extragalactic 3C radio sources mapped at the Cambridge 1-mile telescope, and noted that extended extragalactic radio sources tend to be parallel if they are separated by less than 10deg on the sky. Since 1972, many more radio sources have been mapped with resolutions 10-20 times greater than that of the observations available earlier. The author has therefore reinvestigated this problem in two separate and largely independent samples of some 300 sources each, and reports here that the alignment is present to a high significance level, provided that only the more distant sources are considered. (author)