LERMA UMR8112

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



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Main partners and collaborations

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LERMA develope numerous collaborations both national and international

  • Major agencies and institutions in charge of space missions and major ground-based facilities having collaborations with LERMA: IRAM, ESO, CEA, CNES, ESA, NASA
  • Main collaborating laboratories and institutes: most of Ile-de-France laboratories, in particular members of the 7 “Laboratoires d’Excellence” (LabEx), in which LERMA participates:
    - Plas@Par: Plasma Physics in Paris (UPMC)
    - ESEP: Exploration Spatiale des Environnements Planétaires (Paris Observatory)
    - First-TF: Recherche, Innovation, Formation, Services et Transfert en Temps-Fréquence (CNRS)
    - ICFP: International Center of Fundamental Physics (ENS)
    - ILP: Institut Lagrange de Paris (UPMC)
    - L-IPSL: Labex Institut Pierre Simon Laplace (IPSL)
    - MIChem: Multiscale Interactions in Chemistry (UPMC)

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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