1. Laboratory for High Energy Astrophysics, NASA's Goddard Space Flight Centre, Greenbelt, Maryland 20771, USA

Correspondence to: N. Gehrels Correspondence and requests for materials should be addressed to N. G. (e-mail: Email: gehrels@gsfc.nasa.gov).

One of the great mysteries of the high-energy -ray sky is the group of 170 unidentified point sources^{1, 2} found along the Galactic plane. They are more numerous than all other high-energy -ray sources combined and, despite 20 years of effort, no clear counterparts have been found at other wavelengths. Here we report a new population of such objects. A cluster of 20 faint sources appears north of the Galactic Centre, which is part of a broader class of faint objects at mid-latitudes. In addition, we show in a model-independent way that the mid-latitude sources are distinct from the population of bright unidentified sources along the Galactic plane. The distribution on the sky indicates that the faint mid-latitude sources are associated with the Gould belt^{3, 4} of massive stars and gas clouds at 600 light years distance, as has been previously suggested⁵.