text: In September 2017, a neutrino detector traced back a particle to TXS 0506+056, one of these objects that belongs to their optically polarized BL Lac subtype.
full_question: In September 2017, a neutrino detector traced back a particle to TXS 0506+056, one of these objects that belongs to their optically polarized BL Lac subtype. These objects are found in the center of “Type 1 Seyfert” and “Type 2 Seyfert” entities. Blazars are a class of these objects. A subset of these objects, which usually consist of an accretion disk that surrounds a supermassive black hole, are quasi-stellar objects, or quasars. For 10 points, name these compact, high-luminosity regions found at the center of galaxies.
first_sentence: In September 2017, a neutrino detector traced back a particle to TXS 0506+056, one of these objects that belongs to their optically polarized BL Lac subtype.