NGC 4151

NGC 4151 is an intermediate spiral Seyfert galaxy with weak inner ring structure located 15.8 megaparsecs (52 million light-years) from Earth[4] in the constellation Canes Venatici.

It is one of the nearest galaxies to Earth to contain an actively growing supermassive black hole.

Some astronomers nickname it the "Eye of Sauron" from its appearance.

[9] One supernova has been observed in NGC 4151: SN 2018aoq (Type II-P, mag 15.3).

[10][11] X-ray emission from NGC 4151 was apparently first detected on December 24, 1970, with the X-ray observatory satellite Uhuru,[12] although the observation spanned an error-box of 0.56 square degrees and there is some controversy as to whether UHURU might not have detected the BL Lac object 1E 1207.9 +3945, which is inside their error box – the later HEAO 1 detected an X-ray source of NGC 4151 at 1H 1210+393,[13] coincident with the optical position of the nucleus and outside the error box of Uhuru.

NGC 4151. X-rays (blue), optical data (yellow), radio observation (red)
NGC 4151, by HST (WFC3).
Optical and ultraviolet images of the black hole in the center of NGC 4151
Astronomers using data from the European Space Agency's XMM-Newton satellite have found a long-sought X-ray signal from NGC 4151. When the black hole's X-ray source flares, its accretion disk reflects the emission about half an hour later.