11. At the core, most galaxies have a supermassive black hole, which may result in an active galactic nucleus . 12. At the core is a supermassive black hole, which forms the primary component of an active galactic nucleus . 13. "' SN 1992bd "'was a type II supernova event in 3 east and 93 south of the galactic nucleus . 14. It shows the galaxy NGC 5972, which once had an Active galactic nucleus which has turned off ('off duty'). 15. In the mid-infrared range, the spectrum shows indications of high ionization levels usually associated with an active galactic nucleus . 16. The Galactic Center is marked by an intense inactive galactic nucleus , being estimated at around y " 1. 17. At the core of the galaxy is a low-luminosity active galactic nucleus which has formed an H II region. 18. Due to its relative proximity, large size and active galactic nucleus , Messier 81 has been studied extensively by professional astronomers. 19. The galaxy's location relatively near Earth and its active galactic nucleus make it a commonly studied object for professional astronomers. 20. It has a Seyfert 2 active galactic nucleus , and is one of the most extreme examples of a Seyfert galaxy.
