1ES 1927+654 is a type 2 Seyfert galaxy[1] located 270 million light-years away in the constellation of Draco, containing an active galactic nucleus.

Its sudden changes have made it a target for multi-wavelength observation campaigns, drawing data from X-ray, optical, and radio observatories around the world.

[8] In 2018, detailed observations by X-ray and ultraviolet telescopes revealed that the AGN's accretion disk had undergone a partial or total disruption.

[14] The Quasi-periodic oscillation (QPO) period shrank from 18 to 7.1 minutes over two years, showing unique evolution.

The event challenged models of black hole accretion and inspired new theories about AGN outbursts.