BL Lacertae Objects, or Lacertids, in astronomy, objects in space that are powerful sources of rapidly varying infrared, light, and radio waves. The objects are named after the prototype first observed in the small northern constellation Lacerta (Latin, “the lizard”). The objects are thought to be galaxies that have an active supermassive black hole in the nucleus. The term blazar (short for “blazing star”) has been used for these energetic sources of radiation, which are similar to quasars.