Bahcall–Wolf cusp

Bahcall–Wolf cusp refers to a particular distribution of stars around a massive black hole at the center of a galaxy or globular cluster.

Bahcall and Wolf[3] showed that once this has taken place, the distribution of orbital energies has the form which corresponds to the density ρ=ρ0 r −7/4.

The fully formed cusp[4] extends outward to a distance of roughly one-fifth the supermassive black hole's influence radius.

It is believed that relaxation times in the nuclei of small, dense galaxies are short enough for Bahcall–Wolf cusps to form.

However, no cusp is observed; instead, the density of the oldest stars is flat or even declining toward the Galactic Center.

However, current observations imply a relaxation time at the Galactic Center of roughly 10 billion years, comparable with the age of the Milky Way.

On the other hand, it has been suggested that the distribution of stellar masses at the Galactic Center is "top-heavy", with a much larger fraction of black holes.

The number and distribution of black hole remnants at the Galactic Center is very poorly constrained.