Two ten-billion-solar-mass black holes at the centres of giant elliptical galaxies

Two nearby black holes are the most massive yet found, with masses—of around ten billion solar masses—considerably greater than predicted by conventional methods relating black-hole mass with the stellar velocity dispersion and bulge luminosity of the host galaxy. New 'record' for black hole size At 6.3 billion solar masses, the central black hole in the supergiant elliptical galaxy M87 has been regarded as the most massive known black hole in the Universe for more than three decades. This paper reports two galaxies containing black holes that exceed that figure. NGC 3842 has a central black hole of 9.7 billion solar masses, and NGC 4889 has one of comparable or greater mass. Indications of such massive black holes have existed in the early Universe from luminous quasars but have eluded our detection; these results are the first to connect these early massive black holes to host galaxies in the nearby Universe. Observational work conducted over the past few decades indicates that all massive galaxies have supermassive black holes at their centres. Although the luminosities and brightness fluctuations of quasars in the early Universe suggest that some were powered by black holes with masses greater than 10 billion solar masses 1 , 2 , the remnants of these objects have not been found in the nearby Universe. The giant elliptical galaxy Messier 87 hosts the hitherto most massive known black hole, which has a mass of 6.3 billion solar masses 3 , 4 . Here we report that NGC 3842, the brightest galaxy in a cluster at a distance from Earth of 98 megaparsecs, has a central black hole with a mass of 9.7 billion solar masses, and that a black hole of comparable or greater mass is present in NGC 4889, the brightest galaxy in the Coma cluster (at a distance of 103 megaparsecs). These two black holes are significantly more massive than predicted by linearly extrapolating the widely used correlations between black-hole mass and the stellar velocity dispersion or bulge luminosity of the host galaxy 5 , 6 , 7 , 8 , 9 . Although these correlations remain useful for predicting black-hole masses in less massive elliptical galaxies, our measurements suggest that different evolutionary processes influence the growth of the largest galaxies and their black holes.