apparent visual magnitude of NGC 5548 is approximately 13.3 in the V band.[6]
In 1943, this galaxy was one of twelve
nuclei.[11] Members of this class of objects became known as Seyfert galaxies, and they were noted to have a higher than normal surface brightness in their nuclei.[12] Observation of NGC 5548 during the 1960s with radio telescopes showed an enhanced level of radio emission.[13]Spectrograms of the nucleus made in 1966 showed that the energized region was confined to a volume a few parsecs across, where temperature were around 14000 K and the plasma had a dispersion velocity of ±450 km/s.[14]
Among astronomers, the accepted explanation for the active nucleus in NGC 5548 is the accretion of matter onto a supermassive black hole (SMBH) at the core. This object is surrounded by an orbiting disk of accreted matter drawn in from the surroundings. As material is drawn into the outer parts of this disk, it becomes photoionized, producing broad emission lines in the optical and ultraviolet bands of the electromagnetic spectrum. A wind of ionized matter, organized in filamentary structures at distances of 1–14 light days from the center, is flowing outward in the direction perpendicular to the accretion disk plane.[9]
The mass of the central black hole can be estimated based on the properties of the emission lines in the core region. Combined measurements yield an estimated mass of 6.54+0.26 −0.25×107
optically thick part of the accretion disk at a radius of around 1–2 light days, the X-rays are converted into heat.[16]
14h 17m 59.4s, +25° 08′ 12″
