| Astronomers are puzzled by two vast objects in our galaxy that spew powerful radiation, yet appear pitch black.
The objects are not black holes, which generally are smaller and which, despite their name, do seem to emit visible light, though that light actually comes from around them and not inside them.
The two bizarre objects were detected in a survey of sources within our galaxy of very high-energy gamma rays. Gamma rays are a type of light that is the most powerful known, yet is invisible to our eyes.
The objects appear to be light-years wide, the astronomers said. This would make them bigger than our Solar System
...The newfound objects are also distinct from another, well known type of gamma-ray source called gamma-ray bursts—momentary flashes of gamma rays, detected about once a day, which astronomers think may signal the birth of black holes as dead stars abruptly shrink out of existence. Astronomers have dubbed the mystery objects dark accelerators. | 
