From supernova to something much more intriguing at the core of galaxy 253-3

On 14 November 2014, a bright flash flagged the All Sky Automated Survey for Supernovae, or ASAS-SN — a global network of 20 telescopes managed at Ohio State University in the U.S. The flash originated in galaxy ESO 253-3, located 570 million light-years away.
The sudden burst of energy was examined by astronomers and categorized as a likely supernova and assigned the event designation ASASSN-14ko. Six years later, Anna Payne, a NASA Graduate Fellow at the University of Hawai’i at Mānoa, discovered it was something much different.

While sifting through ASAS-SN data on active galactic nuclei, she discovered a previously unnoticed periodic series of bright flares emanating from galaxy ESO 253-3 — repeating in such a way that led directly back to ASASSN-14ko as the point of first detection.
This was not a supernova as first thought, as a stellar explosion would not repeat at all let alone with such regularity as that observed with ASASSN-14ko.
Anna and her team began to study the phenomenon in more detail, as the possibility emerged that they had found a periodic variable active galactic nuclei — a long sought for entity that could, in part, help astronomers better understand some of the processes ...