H1821+643 is an extraordinarily luminous, radio-quiet quasar in the constellation of Draco.
H1821+643 is an extraordinarily luminous, radio-quiet quasar in the constellation of Draco.
The associated Active Galactic Nucleus (AGN) is situated in the Brightest Central Galaxy (BCG) of a massive (\sim 6.3 \times 10^{14} M_\odot), strong cooling flow cluster, CL 1821+64. Russel et al. (2010) spatially isolated its X-ray signal from the surrounding cluster in Chandra X-ray observatory observations and computed L_\odot = 10^{47} erg/s from the observed X-ray luminosity.
Discovered by embedding cosine similarity (sentence-transformers MiniLM, 384-dim).