A Brief History of AGN

@inproceedings{Shields1999ABH,
  title={A Brief History of AGN},
  author={Gregory Alan Shields},
  year={1999}
}
Astronomers knew early in the twentieth century that some galaxies have emission-line nuclei. However, even the systematic study by Seyfert (1943) was not enough to launch active galactic nuclei (AGN) as a major topic of astronomy. The advances in radio astronomy in the 1950s revealed a new universe of energetic phenomena, and inevitably led to the discovery of quasars. These discoveries demanded the attention of observers and theorists, and AGN have been a subject of intense effort ever since… 

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