Nature 491, 729–731 (2012)

For the known supermassive black holes residing at the centres of massive galaxies, the mass of the black hole is usually 0.1% that of the galactic bulge — the high-density central group of stars in a galaxy, which are normally old, red and of low metallicity. Moreover, the black-hole mass and the velocity dispersion of the stars found in the bulge are empirically related.

So it's a surprise that Remco van den Bosch and colleagues have found a black hole weighing in at 59% of the bulge mass of its host galaxy, NGC 1277, in the constellation Perseus. Based on the average dispersion of 333 km s−1, the predicted mass should be an order of magnitude lower.

Previously, the heavyweight was the black hole in the dwarf galaxy NGC 4486B, at 11% mass. There are, however, five more dense galaxies with high-velocity dispersions, which might host similarly over-massive black holes yet to be observed. Is NGC 1277 an outlier, by 2.1 standard deviations, or will astronomers need to revise the current models of galaxy evolution and black-hole mass relations?