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juin 2018
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George Ellis - On the philosophy of cosmology

Vendredi 1er juin 11:00-12:00

This talk will summarise what we presently know and don’t know about the physical universe, and consider limits to what we probably ever will know due to the unique nature of the universe and existence of observational horizons. It will discuss problems with our current model such as the unknown nature of dark energy and the mechanism of inflation, and the consequent importance of investigating alternative models of the universe and effects such as the backreaction of structure on its evolution. Finally it will consider whether multiverse proposals should be considered as scientific or philosophical proposals.

Michael Gillon (Liège) - The SPECULOOS transit survey : hunting for red worlds

Vendredi 8 juin 11:00-12:00

The thorough characterization of temperate terrestrial exoplanets holds the promise of revolutionizing our understanding of rocky worlds by enabling us to assess their diversity at the galactic scale, not only in terms of orbits, but also in terms of atmospheric compositions, surface conditions, and habitability. In this context, the 1000 brightest ultracool (M7-type and latter) dwarf stars are particularly interesting targets for a transit search, as their proximity combined to their small size and faint luminosity should make possible the characterization of a transiting temperate planet as small as the Earth -and even smaller- with upcoming facilities. In this talk, I will present SPECULOOS (Search for habitable Planets EClipsing ULtra-cOOl Stars), a new photometric survey that aims to explore for transits these faint nearby stars. It is based on a network of 1m-class robotic telescopes whose main nodes will be the SPECULOOS-South and SPECULOOS-North Observatories, each composed of four 1m telescopes optimized for high-precision photometry in the very-near-infrared (0.7 to 1 microns). While the installation of SPECULOOS-North has just been initiated at Teide Observatory (Tenerife), SPECULOOS-South is under commissioning at Paranal Observatory (Chile) and should be fully operational for the end of the year. The high scientific potential of the project was recently established by its discovery of the amazing TRAPPIST-1 (aka SPECULOOS-1) system, of which I will review the ongoing characterization and its exciting perspectives.

Elizabeth Stanway (Warwick) - Understanding Intense Star Formation through Observations and Modelling

Vendredi 15 juin 11:00-12:00

Observations of star-forming galaxies in the distant Universe (z > 2) are starting to confirm the importance of massive stars in shaping galaxy emission and evolution. The intense starbursts common at high redshift, are rare but identifiable in local analogue galaxies. Understanding these populations, and their evolution with age and heavy element content is likely to be key to interpreting processes such as supernova and gamma-ray burst rates, cosmic reionization and the chemical enrichment of the Universe through galaxy-scale winds. It can even be important for the history of habitability on galaxy scales. One avenue of exploring these populations is through the study of local galaxies which share the star formation properties of the distant Universe. A second, overlapping, approach is through modelling. Distant stellar populations are unresolved, and the limited data available must be interpreted in the context of stellar population models. With the upcoming launch of JWST and the promise of observations of galaxies within a billion years of the Big Bang, the uncertainties in modelling massive stars are becoming increasingly important to our interpretation of the high redshift Universe. In turn, these observations of distant stellar populations will provide ever stronger tests against which to gauge the success of, and flaws in, current massive star models.

Margaret Frerking (LESIA) - Imaging Exoplanets with the WFIRST Coronagraph Instrument.

Vendredi 22 juin 11:00-12:00

The WFIRST coronagraph instrument (CGI) will be the first in-space coronagraph using active wavefront control with an expected instrumental raw contrast of 3*10^-9 at 150 milliarcseconds in the V band. The CGI will be capable of directly imaging and spectrally characterizing mature exoplanets in reflected light for the first time. I’m going to present the CGI design architecture, its requirements and expected performance based on laboratory results demonstrated in the High Contrast Imaging Testbed (HCIT) that simulates in-space conditions as well as detailed integrated modeling including the WFIRST telescope predicted performance.

Etienne le Coarer (Univ Grenoble-Alpes) - ImSPOC : a miniaturized imaging spectrometer at the service of the climate

Vendredi 29 juin 11:00-12:00

The ImSPOC (Imaging Spectrometer On Chip) concept is a miniaturization of spectroimagents in the line of
the school of Georges Courtès. Performance does not have to suffer from miniaturization but on the contrary allows
to better specialize them for very different uses. An example is the spectrometer at the origin of NanoCarb.

NanoCarb is a miniaturized space mission for the measurement of major greenhouse gases. It is built around an innovative concept of compact and static Fourier transform imaging spectrometer, developed between ONERA and IPAG these last years [Patent n ° 16 56162, of June 30th, 2016]. The principle is based on a matrix of Fabry-Perot interferometers coupled to an infrared detector, allowing the recording in an image of the spatial and spectral information, without moving elements, for a class of instrument of the order of one kilogram (temperature regulation included ). The objective of the NanoCarb mission is to measure the integrated CO2 on the density column with a statistical error better than 1 ppm, for a spatial resolution of 3km on the ground over 150 km swath. A European funding (H2020 "SCARBO", Space CARBon Observatory) under Airbus Defense & Space aims to study the feasibility of a hybrid constellation based on NanoCarb nano-satellites coupled to a reference mission such as MicroCarb, with the aim of deliver global and daily CO2 emission maps. As part of this project, we are conducting a study with ONERA on the sizing of the instrument and then on the evaluation of its performance. A prototype will then be produced and will be the subject of an airborne measurement campaign after validation tests in the laboratory.

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