I've read that there are 4 distinct although related forms of AGs : Seyferts, Quasars, Radio and Blazars. Are there any other forms possible? Also do these forms ever intermix to give something new?

  • 2
    $\begingroup$ a quick wiki search gives you an answer to all your questions. Try and make your question more specific $\endgroup$ Jun 7, 2014 at 16:36
  • $\begingroup$ This is really a question of semantics. One could say there is just one class. All AGN are supermassive blackholes in which matter is falling in, resulting in energy being dispersed in various forms. Each active galaxy does this a little differently and so you could also subclass into a nearly infinite set of classes. What astronomers use for classes is a somewhat arbitrary but useful set of classes based on where most of the energy is coming out and the strengths of various spectral features. $\endgroup$
    – eshaya
    Oct 7, 2016 at 19:59
  • $\begingroup$ I am not sure if the question is still relevant to the OP. @christopherlovell, the wiki is indeed quite detailed. However, I would point to this excellent review by Paolo Padovani et al. (2017). The AGN zoo is indeed an amazing and intriguing field and the authors have beautifully captured the essense of it. $\endgroup$ Sep 12, 2020 at 14:30

1 Answer 1


Yes of course, there are other forms apart from the four stated above. Basically you have just two kinds:

  1. the radio-quiet, and
  2. the radio-loud.

But then again, there are two Seyferts

  1. Seyfert I, and
  2. Seyfert II

Apart from Quasar, Blazar and Radio galaxy, we also have presently,

  1. BL Lac (Named after its prototype BL Lacarte (original member of Blazar type)), and
  2. OVV (Optically Variable Violent Quasar or OVV Quasar; subtype of Blazar)

Best source to begin with is wikipedia.org of course.

  • $\begingroup$ What you've mentioned are basically the sub forms of the 4 prominent types. Its their inherent characteristics that distinguishes them into sub categories. My question was about any formats apart from these and if an intermix or aby-product (which is an AGN) is possible? $\endgroup$
    – stp30
    May 22, 2014 at 10:45

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