Astronomers discover 21 changing-look active galactic nuclei
(PHYSorg.com Space & Earth)

(Phys.org)-A group of astronomers led by Qian Yang of the Peking University in Beijing, China, has detected 21 active galactic nuclei (AGN) of a rare type known as changing-look AGNs. The finding, reported November 22 in a paper published on arXiv.org, doubles the number of such objects known to date and could improve our understanding of evolution of AGNs.