The Unified Model of active galactic nuclei

This animated infographic provides a simplified representation of the Unified Model of active galactic nuclei or AGNs, energetic sources powered by supermassive black holes that exist at the centre of some galaxies. 

Astronomers have observed different types of AGN. Some, called blazars, are exceedingly bright and can undergo changes in their brightness on timescales of only hours or days while another type, called quasars, are also very bright but tend to be less variable than blazars. Seyfert galaxies, which come in two flavours (1 and 2), are another type of AGN, which are surrounded by host galaxies that are clearly detectable. Seyfert 1 and Seyfert 2 galaxies both have bright cores, but Seyfert 2 tend to be more subdued.   

The Unified Model of AGNs states that despite their differences, all AGNs have the same basic structure: a supermassive black hole surrounded by a thick ring or torus of dust. According to this model, any difference in appearance between AGNs results from the orientation at which we view the black hole and its thick ring from Earth. The type of AGN we see depends on how much the ring obscures the black hole from our view point, completely hiding it in some cases.