= Solution
The differential gravitational field of the <Milky Way> removes loosely bound outer material by <tidal stripping>, giving <globular clusters> and satellite <dwarf galaxies> a characteristic <tidal radius>. For a low-mass satellite of <mass> $m$ on a circular orbit of radius $R$ in a spherical host, the <Jacobi tidal radius> is $r_t\simeq R\{m/[(3-d\ln M_h/d\ln R)M_h(<R)]\}^{1/3}$; eccentric orbits often make the strongest restriction near pericentre. \b[Tidal limitation explains the sharp outer falloff], although escaping stars can form extended <tidal tails>, so a fitted luminosity cutoff is not an exact boundary of all associated material.
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