gravitational pull of a black hole

[Andrew Buren]

Hi, doesn't the gravity of a black hole remain relatively the same? It should because gravitational attraction depends on mass, which stays the same. And if it does, is it posible for a planet to orbit the BH.? (without light, of course)

[Arch2008]

Well the first exoplanet ever discovered orbited a pulsar:
http://en.wikipedia.org/wiki/PSR_B1257+12
PSR B1257+12 is a neutron star with a strong magnetic field that spins so rapidly that it “pulses”. The density of a neutron star is very close to being a black hole and if it accreted mass from a neighbor it would become a black hole. So, yes, a planet could orbit a black hole.

[Nabeshin]

The question isn't really whether or not planets could orbit a BH, but rather, if they could form in a stellar system that will eventually contain a BH. The evidence of exoplanets around pulsars puts at least a lower bound on the stellar mass which will form planetary systems. Since the mass of a star that will form a black hole is just a tad bit higher, it seems likely that these stars could have planetary systems.

[Andrew Buren]

Thanks