Quasar is short for quasi-stellar radio source. The name comes from the fact that the first quasars identified emit mostly radio energy and look much like stars. A radio galaxy is related to, but appears larger than, a quasar. A Seyfert galaxy is a spiral galaxy that emits large amounts of infrared rays as well as large amounts of radio waves, X rays, or both radio waves and X rays. Seyfert galaxies get their name from American astronomer Carl K. Seyfert, who in 1943 became the first person to discover one.
Some active galaxies emit jets and blobs of highly energetic, electrically charged particles.
These particles include positively charged protons and positrons and negatively charged electrons. Electrons and protons are forms of ordinary matter, but positrons are antimatter particles. See Antimatter . The cause of the intense activity in active galaxies is thought to arise from a colossal black hole at the galactic center. The black hole can be as much as a billion times as massive as the sun.