- Sphere of influence (astronomy)
The sphere of influence is a region around a
supermassive black holein which the gravitational potentialof the black hole dominates the gravitational potential of the host bulge.
There are two definitions in common use for the radius of the sphere of influence.The first [Peebles, J. (1972), [http://adsabs.harvard.edu/abs/1972ApJ...178..371P| Star Distribution Near a Collapsed Object] ] is given by
where M is the mass of the black hole, is the stellar velocity dispersion of the host bulge, and is the
gravitational constant. The second definition [Merritt, D. (2004), [http://adsabs.harvard.edu/abs/2004cbhg.symp..263M| Single and Binary Black Holes and their Influence on Nuclear Structure] ] is the radius at which the enclosed mass in stars equals twice M, i.e.
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