Using globular clusters to test gravity in the weak acceleration regime

TL;DR

This study tests Newtonian gravity in low acceleration regimes using globular clusters, finding they behave like galaxies with flat velocity dispersion profiles, challenging current gravity models.

Contribution

It demonstrates that globular clusters exhibit galaxy-like behavior in low acceleration regimes, suggesting potential modifications to gravity theories.

Findings

Velocity dispersion profiles flatten at low accelerations.

Globular clusters lack dark matter, yet show galaxy-like dynamics.

Results imply possible need to revise gravity theories in weak regimes.

Abstract

We report on the results from an ongoing program aimed at testing Newton's law of gravity in the low acceleration regime using globular clusters. It is shown that all clusters studied so far do behave like galaxies, that is, their velocity dispersion profile flattens out at large radii where the acceleration of gravity goes below 1e-8 cm/s/s, instead of following the expected Keplerian fall off. In galaxies this behavior is ascribed to the existence of a dark matter halo. Globular clusters, however, do not contain dark matter, hence this result might indicate that our present understanding of gravity in the weak regime of accelerations is incomplete and somehow incorrect.