Unidentified Sources

3rd EGRET Catalog

More than 60% of the observed high-energy gamma-ray sources are unidentified. 172 of the 271 sources in the Third EGRET Catalog still have yet to been identified. Possible candidates for these sources include active galactic nuclei, pulsars, supernova remnants, dense molecular clouds, and stellar-mass black holes within our Galaxy. It is even quite possible that entirely new phenomena could account for some portion of these unidentified sources.

GLAST will address the mystery of the unidentified sources in two ways. First, the higher sensitivity of GLAST will allow searches for pulsars with unknown pulse period, rather than relying on radio or X-ray discovery. Second, GLAST will localize the positions of the unidentified sources accurately enough to make searches for counterparts at other wavelengths much more feasible.