IS THE 5-KPC GALACTIC ARM A COLONY OF X-RAY PULSARS

MORE than two dozen binary X-ray pulsars have been discovered in our Galaxy1. Because of instrumental constraints, however, most of these have been discovered within only a few kiloparsecs (kpc) of the Sun. Here we report the discovery by the Ginga satellite of four X-ray pulsars and three hard X-ray sources in the galactic plane at galactic latitude l≈30°and a distance of about 10 kpc (the '5-kpc arm '2). This indicates that the 5-kpc arm has been the site of vigorous formation of X-ray pulsars, and that in general their distribution might be expected to be non-uniform. © 1990 Nature Publishing Group.