LERMA UMR8112

Laboratoire d’Études du Rayonnement et de la Matière en Astrophysique et Atmosphères



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May 3rd

by Valerie Audon - published on


Conseil de laboratoire du LERMA
3 mai 2016 à 9h30
Observatoire de Paris
Salle du Conseil
77, avenue Denfert Rochereau
75014 Paris
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ORDRE DU JOUR



I Approbation de l’ordre du jour



II Approbation du compte rendu du Conseil de laboratoire du 18 janvier 2016



III Informations du Directeur



IV Campagne emploi 2017



V Validation de la procédure d’évaluation des demandes de Visiteurs longue durée



VI Missions du directeur technique



VI Questions diverses


Relevé de conclusions
Compte rendu

Séminaires à venir

Vendredi 20 septembre 2019, 14h00
Atelier, Paris
Challenging a Newtonian prediction through Gaia wide binaries
Xavier HERNANDEZ
UNAM, Mexico
résumé :
Under Newtonian dynamics, the relative motion of the components of a binary star should follow a Keplerian scaling with separation. Once orientation effects and a distribution of ellipticities are accounted for, dynamical evolution can be modelled to include the effects of Galactic tides and stellar mass perturbers. This furnishes a prediction for the relative velocity between the components of a binary and their projected separation. After reviewing recent work evidencing the existence of a critical acceleration scale in Elliptical Galaxies and Globular Clusters, I will show new results showing such a phenomenology in Gaia wide binaries using the latest and most accurate astrometry available. The results are consistent with the Newtonian prediction for projected separations below 7000 AU, but inconsistent with it at larger separations, where accelerations are expected to be lower than the critical a0 value of MONDian gravity. This result challenges Newtonian gravity at low accelerations and shows clearly the appearance of gravitational anomalies of the type usually attributed to dark matter at galactic scales, now at much smaller stellar scales.


 
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