The stellar collider in the Galactic Center
The potential for probing a new regime of stellar dynamics near the MBH in the Galactic Center is best illustrated by comparing the collisional timescale there with that in the cores of the densest globular clusters, which for a long time served as laboratories for the study of collisional processes. In a dense globular cluster, n_* ∼ 10⁶ M_ּ pc⁻³ and σ ∼ 10 km s⁻¹, whereas in the Galactic Center, the density may be as high as n_* ∼ 10⁸ M_ּ pc⁻³ and σ ∼ 1000 km s⁻¹. The timescale for collisions between solar-type stars in a globular cluster can be estimated to be almost 10¹⁰ yr, roughly the age of the Galaxy and of a solar-type star, whereas it is only ∼5×10⁸ yr in the inner 0.02 pc of the Galactic Center. These estimates imply that while physical collisions are only marginally relevant in the cores of the densest globular clusters, they completely dominate the dynamics in the innermost part of the MBH cusp.