| Abstract |
Without doubt, planets are formed from proto-planetary disks around stars, and about four thousand exoplanets have been discovered until now. However, proto-planetary disks may not be the only site of forming planets in the universe. Here we propose a novel site for planet formation, namely circumnuclear gas disks around supermassive black holes (SMBHs). Most galaxies harbor SMBHs whose masses are ranged from a few million to billion solar masses. Accretion disks around SMBHs emit enormous energy owing to mass accretion to the SMBHs, which are known as the `central engine' of active galactic nuclei (AGNs). They are believed to be surrounded by dense, dusty gas, which obscures the emission from the accretion disks. As a result, there should be a cold dust disk beyond several parsecsfrom the AGN. Here we investigate growth history from sub-micron sized icy monomers to km-sized planetesimals in circumnuclear disks around SMBHs, based on recent plausible theories of planetesimal formation around stars. We found that numerous (> 10^4 pc^-2) "blanets" = black hole planets could be hidden around some AGNs. |
