2003/05/21 by R. Scarpa, Riccardo Scarpa, G. Marconi +3 · 6 citations
Physics and Astronomy · #Galaxies: Formation, Evolution, Phenomena #Solar and Space Plasma Dynamics #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1051/0004-6361:20030762
published as Astron.Astrophys.405:L15,2003 · Accepted for publication on A&A Letters. Four pages + 2 figures
arxiv created 2003/05/21 · openalex publication_date 2003/06/16 · arxiv updated 2011/05/23 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/31
We have carried out a study of the velocity dispersion of the stars in the outskirts of the globular cluster ω Cen, finding that the velocity dispersion remains constant at large radii rather than decrease monotonically. The dispersion starts to be constant for an acceleration of gravity of cm s-2. A similar result is obtained reanalyzing existing data for the globular cluster M15 where the profile flattens out for cm s-2. In both cases the acceleration is comparable to that at which the effect of dark matter becomes relevant in galaxies. Explanations for this result within Newtonian dynamics exist (e.g. cluster evaporation, tidal effects, presence of dark matter) but require ad hoc tuning of the relevant parameters in order to make in both clusters the dispersion profile flat starting exactly at the same acceleration. We suggest that this result, together with a similar one for Palomar 13 and the anomalous behavior of spacecrafts outside the solar system, may indicate a breakdown of Newton's law in the weak acceleration regime. Although not conclusive, these data prompt for the accurate determination of the internal dynamics of as many GCs as possible.