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The stars orbiting the compact radio source Sgr A* in the Galactic Centre areprecision probes of the gravitational field around the closest massive blackhole. In addition to adaptive optics assisted astrometry (with NACO / VLT) andspectroscopy (with SINFONI / VLT, NIRC2 / Keck and GNIRS / Gemini) over threedecades, since 2016/2017 we have obtained 30-100 mu-as astrometry with thefour-telescope interferometric beam combiner GRAVITY / VLTI reaching asensitivity of mK = 20 when combining data from one night. We present thesimultaneous detection of several stars within the diffraction limit of asingle telescope, illustrating the power of interferometry. The new data forthe stars S2, S29, S38 and S55 yield significant accelerations between Marchand July 2021, as these stars pass the pericenters of their orbits between 2018and 2023. This allows for a high-precision determination of the gravitationalpotential around Sgr A*. Our data are in excellent agreement with generalrelativity orbits around a single central point mass, M = 4.30 x 10^6 M_sunwith a precision of about +-0.25%. We improve the significance of our detectionof the Schwarzschild precession in the S2 orbit to 7 sigma. Assuming plausibledensity profiles, an extended mass component inside S2's apocentre (= 0.23" or2.4 x 10^4 R_S) must be 3000 M_sun (1 sigma), or 0.1% of M. Adding the enclosedmass determinations from 13 stars orbiting Sgr A* at larger radii, theinnermost radius at which the excess mass beyond Sgr A* tentatively is seen isr = 2.5" >= 10x the apocentre of S2. This is in full harmony with the stellarmass distribution (including stellar-mass black holes) obtained from thespatially resolved luminosity function.

The mass distribution in the Galactic Centre from interferometric astrometry of multiple stellar orbits