In Wada , Tsukamoto , and Kokubo ( 2019 ) , we proposed for the first time that a new class of planets , blanets ( i.e. , black hole planets ) , can be formed around supermassive black holes ( SMBHs ) in the galactic center .
Here , we investigate the dust coagulation processes and physical conditions of the blanet formation outside the snowline ( r _ { snow } \sim several parsecs ) in more detail , especially considering the effect of the radial advection of the dust aggregates .
We found that the viscous \alpha -parameter in the turbulent circumnuclear disk should be smaller than 0.04 , to prevent the destruction of the aggregates due to collisions .
The formation timescale of blanets \tau _ { GI } at r _ { snow } is , \tau _ { GI } \simeq 70-80 Myr for \alpha = 0.01 - 0.04 and M _ { BH } = 10 ^ { 6 } M _ { \odot } .
The mass of the blanets ranges from \sim 20 M _ { E } to 3000 M _ { E } in r < 4 pc for \alpha = 0.02 ( M _ { E } is the Earth mass ) , which is in contrast with 4 M _ { E } -6 M _ { E } for the case without the radial advection .
Our results suggest that blanets could be formed around relatively low-luminosity AGNs ( L _ { bol } \sim 10 ^ { 42 } erg s ^ { -1 } ) during their lifetime ( \lesssim 10 ^ { 8 } yr ) .