NASA and Italian scientists using Swift have for the first time determined what the particle jets streaming from black holes are made of. Black hole particle jets are commonly seen in quasars and other celestial objects, shooting off at nearly light speed. According to the Swift team, these jets appear to be made of protons and electrons, solving a mystery as old as the discovery of jets themselves in the 1970s. The jets observed by Swift contain about the mass of Jupiter if it were pulverized and blasted out into intergalactic space.
https://www.nasa.gov/centers/goddard/news/topstory/2006/swift_blazars.html