Archives Séminaires 2013-2014

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Séminaire IPAG de Johannes Sahlmann (ESA), jeudi 20 février 2014 à 11h00, IPAG seminar room

Measuring the positions of nearby stars can inform us on the presence and properties of extrasolar planets around them, because planets induce an orbital reflex motion on the host star. The typical amplitudes of this effect are in the range of 0.1 milli-arcseconds and smaller over timescales of years, which are challenging figures for present-day instruments. I will present an overview of the observing techniques that can reach the necessary precision, which include large ground-based (…)

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Séminaire IPAG de Hans Zinnecker (Sofia Obs.), jeudi 27 février 2014 à 11h00, IPAG seminar room

SOFIA, short for Stratospheric Observatory for Infrared Astronomy, is a Boeing 747SP aircraft with a 2.7m telescope flying as high as 45000 ft in the stratosphere above 99 percent of the precipitable water vapor. SOFIA normally operates from its base in Palmdale, California, and a typical observing flight lasts for 10 hours before returning to base. In this talk, I will present a few highlights of SOFIA early science and its future potential, when the full suite of 7 instruments will be (…)

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Séminaire IPAG de Frederic Vincent (Centre Astronomique Copernic, Warsaw), jeudi 13 mars 2014 à 11h00, IPAG seminar room

Studying variable phenomena in the vicinity of black holes is interesting as it allows to better understand physics in strong gravitational fields. It may also lead in the distant future to observationally probing spacetime in the very vicinity of a compact object, thus testing the predictions of general relativity in its most extreme regime. Radiation flares at the Galactic center are an example of such variable phenomena. I will analyze the ability of the very near future (first light May (…)

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Séminaire IPAG de Guillaume Laibe (University of St Andrews), jeudi 20 mars 2014 à 11h00, IPAG seminar room

The solid material found in planets was initially present in the form of dust particles in protoplanetary discs. Explaining how those small bodies can grow so efficiently challenges the astrophysicists for decades. In this context, I will first present some recent theoretical results on the coupling between growth and radial migration of grains in those discs. I will then discuss the numerical challenges related to two-fluids (gas and dust) simulations, highlighting some fundamental (…)

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Séminaire IPAG de David Charbonneau (Harvard), jeudi 3 avril 2014 à 11h00, IPAG seminar room

The investigation of planets orbiting other stars has moved from the study of gas giants to the hunt for smaller planets that are predominantly rock and ice in composition. When such planets are discovered in edge-on orbits, such that the planet and star undergo mutual eclipses, we are granted the opportunity to determine directly the planetary masses and sizes. Most interestingly, we can study starlight filtered through the planetary atmosphere to deduce its chemical composition, and (…)

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Séminaire IPAG de Edwige Chapillon (IRAM), jeudi 10 avril 2014 à 11h00, IPAG seminar room

Understanding the structure and evolution of disks surrounding young low-mass stars is one of the key issues to study the process of planet formation. Observation of molecular lines is a useful tool to constrain the disks physical structure, as different molecules sample different physical conditions. Beside the abundant CO, several other molecules have been detected in the outer part of the disks in the millimeter domain (e.g. HCO+, H2CO, CS, HCN, CN...). In this talk I will present results (…)

Séminaire exceptionnel

Séminaire IPAG de Roland Bacon (CRAL) & Gérard Zins (IPAG), mardi 15 avril 2014 à 10h30, IPAG seminar room

The Multi Unit Spectroscopic Explorer (MUSE) is a second-generation VLT panoramic integral-field spectrograph. MUSE has a field of 1×1 arcmin² sampled at 0.2×0.2 arcsec² and a simultaneous spectral range of 0.465-0.93 µm, at a resolution of R 3000. The instrument has been designed to take advantage of the VLT ground layer adaptive optics ESO facility using four laser guide stars. MUSE couples the discovery potential of a large imaging device to the measuring capabilities of a high-quality (…)

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Séminaire IPAG de Nicolas Martin (Strasbourg Obs.), jeudi 24 avril 2014 à 11h00, IPAG seminar room

The salience of satellite dwarf galaxies for understanding galaxy formation in a cosmological context has been made all the more evident in the past decade with the discovery of numerous faint Local Group galaxies. These faint systems are not only important to understand the faint end of galaxy formation but also their distribution around their host can test the hierarchical formation induced by the favored cosmological paradigm. I will review our successful effort to mine the two most (…)

Séminaire exceptionnel

Séminaire IPAG de T.A. ten Brummelaar Associate Director of CHARA, mardi 29 avril 2014 à 11h00, IPAG seminar room

The CHARA Array is a six telescope optical and near infrared interferometer run by Georgia State University and located at Mount Wilson Observatory just north of Los Angeles. The CHARA consortium includes the University of Michigan, l’Observatoire de Paris, The University of Sydney, Observatoire de la Cote d’Azur, The NASA Exoplanet Science Institute, The Max Planck Institute for Radio Astronomy, and soon I hope the JMMC. In this talk I will give a brief overview of the facility as well as (…)

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Séminaire IPAG de Alexis Carlotti (IPAG), jeudi 15 mai 2014 à 11h00, IPAG seminar room

NASA recently acquired two "Hubble class" 2.4m mirror telescopes from the national reconnaissance office One - WFIRST-AFTA - was swiftly chosen to replace the previously cancelled 0.7m WFIRST telescope, with a new launch scheduled for 2021. A wide-field imaging camera with a grism and an IFU spectrograph will be used to address the main scientific objectives of WFIRST : searching for dark energy, and surveying exoplanets through microlensing. The much larger diameter of WFIRST-AFTA has also (…)