Archives Séminaires 2012-2013

Séminaire

Séminaire IPAG de Cecilia Ceccarelli (IPAG), jeudi 14 février 2013 à 11h00, IPAG seminar room

I will provide a brief overview of the pas ESA missions and a more extended picture of the present missions. However, the goal of the presentation is giving a picture of the already planned future missions and, mostly important, the plans for the next selections and calls, based on my "observatory" as member of the ESA Astronomical Working Group and Vlodlek’s experience in the ESA SSEWG and SSAC groups. So please come with questions too. I’ll try to answer.

Séminaire

Séminaire IPAG de Mickael Bonnefoy (MPIA), jeudi 21 février 2013 à 11h00, IPAG seminar room

Abstract : High contrast imaging is the only viable technique nowadays to probe the population of wide (> 5 AU) giant planets and brown dwarfs around young stars (< 150 Myr) of the solar neighborhood (d < 100 pc). Recent breakthrough detections of gaseous companions at relatively short separations (8-78 AU) around young early-type stars (HR 8799, β Pictoris) with this technique have motivated new surveys to look for gas giant planets around similar or even more massive (B-type) stars. (…)

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Séminaire IPAG de Johan Olofsson (MPIA), jeudi 7 mars 2013 à 11h00, IPAG seminar room

I will present recent results regarding two peculiar objects in which planetary formation is most likely on-going. First, I will discuss in detail the 7 Myr old transition disk around TCha. With a large interferometric dataset, we are able to finely characterize the geometry of this transition disk, and revisit the previous detection of a candidate companion found to be in the gap. Nonetheless, the disk displays several features indicating that giant planet formation is on-going. Second, I (…)

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Séminaire IPAG de Matthieu Gounelle (MNHN), jeudi 14 mars 2013 à 11h00, IPAG seminar room

When meteorites formed, 4.5 Gyr ago, they contained short-lived radio nuclides (SLRs) such as 26Al (T1/2 = 0.64 Myr), 60Fe (T1/2 = 2.6 Myr) or 182Hf (T1/2 = 9 Myr). The origin of these radio elements and their astrophysical relevance has long been elusive. I will show that the presence of SLRs with a diversity of half-lives in the solar protoplanetary disk is nothing else but the fossilized record of sequential star formation within a hierarchical interstellar medium (ISM). This finding (…)

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Séminaire IPAG de Philippe Delorme (IPAG), jeudi 21 mars 2013 à 11h00, IPAG seminar room

To investigate whether formation of large separation planets is correlated with stellar host mass, we systematically imaged young M dwarfs of the solar neigbhourhood with NACO adaptive optic imager at VLT. We applied the latest central star removal technics (ADI, LOCI...) to search for Jupiter mass planets around this sample. We present here what we found and what we did not found after 2 years of survey.

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Séminaire IPAG de Françoise Combes (IAP), jeudi 28 mars 2013 à 11h00, IPAG seminar room

The "standard" model of cold dark matter LCDM is today the best to account for the formation of large-scale structures of the universe. However, there remain unsolved problems at the scale of galaxies. The distribution of baryons and dark matter in galaxies predicted by numerical simulations is far from what is observed. The model predicts a large excess of dark matter in galaxies, and a large number of satellites, with orders of magnitude discrepancy with observations. I will discuss how (…)

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Séminaire IPAG de Robert Pascal (Université Montpellier) , jeudi 4 avril 2013 à 11h00, IPAG seminar room

Sixty years after the publications of the double helix structure of DNA and the Miller-Urey experiment, there is still no accepted scientific analysis of the origin of life process. Jacques Monod in “Le hasard et la nécessité” believed that the origin of life was an intrinsically improbable contingent event. But is it scientifically acceptable to give up researching considering that life originated from a violation of the 2nd Law ? With the discovery of exoplanets similar to the Earth, it is (…)

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Séminaire IPAG de Jean-Philippe Uzan (IAP), jeudi 11 avril 2013 à 11h00, IPAG seminar room

Fundamental constants are a cornerstone of our physical laws. Any constant varying in space and/or time would reflect a violation of the equivalence principle. Thus, it is of importance for our understanding of gravity and of the domain of validity of general relativity to test for their constancy. I will first recall the relations between the constants, the tests of the local position invariance and of the universality of free fall. I will then sketch the main theoretical frameworks in (…)

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Séminaire IPAG de Pierre Encrenaz (Obs. Paris), jeudi 18 avril 2013 à 11h00, IPAG seminar room

La sonde Cassini permet de suivre l’evolution des lacs de methane sur Titan, en particulier leur niveau. L evaporation ne peut expliquer seule une baisse de profondeur de 4m en 5 ans .un mouvement de l’alkanofer semble necessaire . L absence de vagues est aussi incomprise ,alors que l existence de dunes prouve la presence de vents.

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Séminaire IPAG de Jay Fahiri (Cambridge), jeudi 16 mai 2013 à 11h00, IPAG seminar room

We now stand firmly in the era of solid exoplanet detection via Kepler and other state of the art facilities. Yet the empirical characterization of these most intriguing planets is extremely challenging. Transit plus radial velocity data can yield planet mass and radius, and hence planet density, but the bulk composition remains degenerate and model-dependent. The abundances of a handful of exoplanet atmospheres can be estimated from transit spectroscopy, but probing only the tenuous outer (…)