LERMA UMR8112

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



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February 20th

by Valerie Audon - published on


Conseil de laboratoire du LERMA
20 Février 2017 à 9h30
Salle Danjon
Observatoire de Paris
61, avenue de l’Observatoire
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 05 Décembre 2016


III Informations du directeur (Darek Lis)


IV Approbation de la demande de tutelle avec l’Université Paris Diderot (P7) (Darek Lis)



V Présentation du budget 2017 (Darek Lis)



VI Discussion autour du projet quinquennal présenté à l’Assemblée Générale (Franck Le Petit et Jean-Hugues Fillion)



VII 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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