Agenda de Lagrange
!! Science - Les modes de gravité solaires révèlent une rotation rapide de son cœur thermonucléaire  en savoir plus...
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    L’instrument GOLF à bord de la sonde SOHO, collaboration entre l’ESA et la NASA lancée en 1995, est entièrement dédié à la mesure des oscillations solaires dont les modes de gravité, porteurs des propriétés physiques des couches solaires les plus profondes. La signature des modes de gravité est cependant très faible en surface et plus de 20 ans de recherche n’avaient pas permis de les détecter avec certitude. C’est en regardant « ailleurs et autrement » qu’Éric Fossat (Astronome émérite au Laboratoire Lagrange, Observatoire de la Côte d’Azur) et ses collègues (OCA, IAS, CEA et Observatoire de Bordeaux en France, IAC en Espagne et UCLA aux Etats-Unis) ont enfin réussi à mettre en évidence leur signature, qui ne souffre plus d’aucune ambiguïté.

Août 2017

Séminaire Lagrange
Physical properties of L-type asteroids: a link to the primordial Solar System?
 mardi 29 août 2017, 10h30, NEF - Mont Gros - CION - talk in english - retransmis à Valrose
Maxime Devogele - OCA/U. Liège
A few years ago, asteroid polarimetry allowed to discover a class of asteroids exhibiting peculiar phase polarization curves, collectively called "Barbarians" from the prototype of this class, the asteroid (234) Barbara.
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    All such objects belong to the L visible plus near infrared based taxonomic class. The anomalous polarization has been tentatively interpreted in terms of high-albedo, spinel-rich Calcium-Aluminum inclusions (CAI) which could be abundant on the surfaces of some of these asteroids, according to their spectral reflectance properties and to analogies with CO3/CV3 meteorites. Such CAIs are thought to be among the oldest mineral assemblages ever found in the Solar System. Barbarians' surfaces could therefore be rich in this very ancient material and bring information on the early phases of planetary formation. Based on such information, a systematic campaign for photometric, polarimetric and spectroscopic characterization has been conducted. These observation campaigns allowed to improve our general knowledge about these peculiar asteroids and highlight the link between polarization and polarimetric properties. As it was suggested, a link between the presence of CAI and the polarimetric response was found. Our observations show that the relative abundance of CAI is correlated with the polarimetric inversion angle. This is the first time that a direct link between polarimetric and spectroscopic properties is found.

Septembre 2017

Séminaire Lagrange
 mardi 5 septembre 2017, 10h30
Simon Thalabard - OCA
Séminaire Lagrange
Cosmic Anisotropies from Quasars
 mardi 12 septembre 2017, NEF - Mont Gros - CION - talk in english - retransmis à Valrose
Vincent Pelgrims - LPSC Grenoble
Large-scale correlations of the position angles of the polarization vectors of the light form quasars were discovered almost twenty years ago. These correlations take place over giga parsec scale distances. Due
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    to their extreme-scale nature these observations have been recognized as potentially competing the isotropy of the well-accepted concordance cosmological model. Later these observations have been confirmed and the correlation signal enhanced by means of additional data. After a review of the main features of those large-scale polarization alignments, I shall present the related results that I obtained. Therefore, I shall address two types of unexpected, but observed, correlations that involve the orientation of the linear polarization vectors of the light of quasars, at optical and radio wavelengths. First, the quasar polarization vectors appear to be coherently oriented to one another over very large scales and, second, their orientations are found to be correlated with specific directions defined by the quasar spatial distribution. I will discuss a tentative interpretation of the data following which the polarization correlations reflect the coevolution of the black hole spin axes with —and within— the cosmic web.
Séminaire Lagrange
Exoplanet formation in the Galaxy: different environments, different planets
 mardi 19 septembre 2017, 10h30, NEF - Mont Gros - CION - talk in english - retransmis à Valrose
Adibekyan Vardan
Séminaire Lagrange
Cosmic tsunamis and tornadoes
 mardi 26 septembre 2017, 10h30, NEF - Mont Gros - CION - talk in english - retransmis à Valrose
Andra Stroe - ESO Garching
Red weather alert: dangerous cosmic weather forecast, in light of galaxy cluster mergers! Clusters grow through mergers with other clusters, events which give rise to the largest cosmic shock waves, as
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    well as turbulence. Shocks travel like giant tsunamis through the cluster galaxies and the electron plasma between them, while turbulence stirs the intra-cluster medium. By bringing together optical, radio and HI data, I will discuss how merger shocks and turbulence shape the evolution of cluster galaxies and reverse typical environmental trends. I will highlight how shock-induced star formation may a fundamental driver not only in the evolution of low-z clusters, but also in the context of proto-clusters and high-redshift clusters, where mergers and shocks were far more common than in the nearby Universe.

Octobre 2017

Séminaire Lagrange
Magnetic Atoms in the Universe
 mardi 3 octobre 2017, 10h30, NEF - Mont Gros - CION - talk in english - retransmis à Valrose
BURDYUZHA Vladimir - Physical Institute of Russian Academy of Science
Séminaire Lagrange
A Global View of Star Formation in the Milky Way
 mardi 10 octobre 2017, 10h30, NEF - Mont Gros - CION - talk in english - retransmis à Valrose
Karl Menten - Max-Planck-Institute for Radio Astronomy
Stars with more than about ten solar masses dominate galactic ecosystems. Understanding their formation is one of the great challenges of modern astronomy. The spectacular HII regions they excite delineate the
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    spiral arms of galaxies such as our own – making it clear that star formation and Galactic structure are intimately related. We report on an ambitious program that consists of a powerful multi-pronged approach to study star formation over the whole Milky Way. The BeSSeL survey, VLBI observations of maser sources associated with young protostars, delivers distances by trigonometric parallax to most of the dominant star forming regions in the Galaxy. These allow characterizing its spiral structure and luminosity and mass determinations. Submillimeter emission from dust surveyed over the whole Southern Galactic plane with the APEX telescope delivers the locations of deeply embedded protostars and protoclusters and their masses. In a comprehensive follow-up program we are studying the energetics, chemistry and kinematics of their gaseous content and (with ALMA) zoom in on them. At longer wavelengths, in a very sensitive survey with the newly expanded Karl G. Jansky Very Large Array we image the radio emission of the whole (northern) Galactic plane with arc second resolution and also find masers and hyper- and ultracompact HII regions, pinpointing the very centers of early star-forming activity. Moreover, we are studying the infrared emission from more developed massive star clusters. Our synoptic approach is using some of the world’s premier observatories to create a coherent, global perspective on star formation in our Galaxy.
Séminaire Lagrange
Spin-Alignment of Stars in old open clusters
 mardi 17 octobre 2017, 10h30, NEF - Mont Gros - CION - talk in english - retransmis à Valrose
Enrico Corsaro - INAF

Novembre 2017

Séminaire Lagrange
Histoire de la Nucléosynthèse stellaire
 mardi 14 novembre 2017, de 10h00 à 12h00, NEF - Mont Gros - CION - présentation en français - retransmis à Valrose
Nicolas Prantzos - IAP
Séminaire Lagrange
 mardi 21 novembre 2017, 10h30, NEF - Mont Gros - CION - talk in english - retransmis à Valrose
Jaccopo Chevallard - ESTEC

Décembre 2017

Séminaire Lagrange
 mardi 12 décembre 2017, 10h30, NEF - Mont Gros - CION - talk in english - retransmis à Valrose
Fernando Buitrago - Astronomical Observatory of Lisbon

Mise à jour : 19/08/17 01:28