What does the S2 star's orbit tell us about dark matter near Sgr A*?

Using precise measurements of the S2 star's orbit around Sgr A*, the authors constrain the density profile of a dark matter halo surrounding the supermassive black hole, fitting a generalized Dehnen-type model via MCMC analysis. The best-fit halo slope parameter comes out near γ ≈ 1.2, with tight upper bounds on halo density and scale radius. It's a clean demonstration that stellar orbital mechanics — specifically the perihelion shift over one orbit — can probe dark matter distributions that would otherwise be invisible.