Capture d’écran 2025-03-16 003105

The observational difference between a standard AGN (left) and a dying AGN (right) discovered by Ichikawa et al. In the dying AGN, the nucleus is very faint in all wavelength bands because AGN activity is already dead, while the extended ionized region is still visible for about 3,000 light-years since it takes about 3,000 years for the light to cross the extended region. (Image credit: Ichikawa et al.)