A chemical survey of exoplanets with ARIEL

Thousands of exoplanets have now been discovered with a huge range of masses, sizes and orbits: from rocky Earth-like planets to large gas giants grazing the surface of their host star. However, the essential nature of these exoplanets remains largely mysterious: there is no known, discernible pattern linking the presence, size, or orbital parameters of a planet to the nature of its parent star. We have little idea whether the chemistry of a planet is linked to its formation environment, or whether the type of host star drives the physics and chemistry of the planet’s birth, and evolution. ARIEL was conceived to observe a large number (~1000) of transiting planets for statistical understanding, including gas giants, Neptunes, super-Earths and Earth-size planets around a range of host star types using transit spectroscopy in the 1.25–7.8 μm spectral range and multiple narrow-band photometry in the optical. ARIEL will focus on warm and hot planets to take advantage of their well-mixed atmospheres which should show minimal condensation and sequestration of high-Z materials compared to their colder Solar System siblings. Said warm and hot atmospheres are expected to be more representative of the planetary bulk composition. Observations of these warm/hot exoplanets, and in particular of their elemental composition (especially C, O, N, S, Si), will allow the understanding of the early stages of planetary and atmospheric formation during the nebular phase and the following few million years. ARIEL will thus provide a representative picture of the chemical nature of the exoplanets and relate this directly to the type and chemical environment of the host star. ARIEL is designed as a dedicated survey mission for combined-light spectroscopy, capable of observing a large and well-defined planet sample within its 4-year mission lifetime. Transit, eclipse and phase-curve spectroscopy methods, whereby the signal from the star and planet are differentiated using knowledge of the planetary ephemerides, allow us to measure atmospheric signals from the planet at levels of 10–100 part per million (ppm) relative to the star and, given the bright nature of targets, also allows more sophisticated techniques, such as eclipse mapping, to give a deeper insight into the nature of the atmosphere. These types of observations require a stable payload and satellite platform with broad, instantaneous wavelength coverage to detect many molecular species, probe the thermal structure, identify clouds and monitor the stellar activity. The wavelength range proposed covers all the expected major atmospheric gases from e.g. H2O, CO2, CH4 NH3, HCN, H2S through to the more exotic metallic compounds, such as TiO, VO, and condensed species. Simulations of ARIEL performance in conducting exoplanet surveys have been performed – using conservative estimates of mission performance and a full model of all significant noise sources in the measurement – using a list of potential ARIEL targets that incorporates the latest available exoplanet statistics. The conclusion at the end of the Phase A study, is that ARIEL – in line with the stated mission objectives – will be able to observe about 1000 exoplanets depending on the details of the adopted survey strategy, thus confirming the feasibility of the main science objectives.Peer reviewedFinal Published versio

La catalyse par les triflates et triflimidures métalliques (réaction d'allylation de Friedel-Crafts et alkenylation intramoléculaire)

Les composes aromatiques polyfonctionnalisés constituent une importante classe d intermédiaires et peuvent présenter un intérêt non seulement dans le domaine pharmaceutique, mais aussi dans la chimie des arômes et parfums. L objectif de ce travail concerne la mise au point d une méthode catalytique permettant les réactions d allylation de composés aromatiques par réaction de Friedel-Crafts et des réactions de cyclisation intramoléculaire. Les triflates métalliques [M+n(OSO2CF3)n], des acides de Lewis forts, sont considérés comme des superacides de Lewis. L allylation de nombreux composés aromatiques a été développée en utilisant des acétates d allyle comme réactifs. La méthode nécessite un petite quantité d In(OTf)3 (1 % molaire), s effectue à température ambiante et les molécules cibles sont obtenues avec des rendements compris entre 50 et 90 %. La réaction catalytique d allylation sur des dérives phénoliques a aussi été étudiée. Les produits de cyclisation intramoléculaire ont été obtenus avec de bons rendements. Cette même méthode est appliquée dans le cas de réaction de Friedel-Crafts type alkénylation intramoléculaire. Les produits ont été obtenus quantitativement. Une étude complémentaire avec un composé allylique chiral ainsi que d autres réactions ont permis de proposer des mécanismes réactionnels.Aromatic polyfunctionalised compounds constitute an important class of intermediates and may present a wide scope of applications not only in the pharmaceutical field, but also in flavour and fragrance chemistry. The scope of this work was focused on the elaboration of a catalytic system promoting allylation of aromatics compounds by Friedel-Crafts method and intramolecular cyclisation reaction. Trifluoromethanesulfonate catalysts [M+n(OSO2CF3)n] are strong Lewis acids, considered as Lewis superacids . The allylation of various aromatic compounds, using acetates as the allylating agents has been developed. The method requires only a low amount of In(OTf)3 (1 mol%), operate at room temperature and the target molecules are obtained in yields of 50-90%. Allylation reactions with phenol derivatives have also been examined in catalytic reactions. Products involving intramolecular cyclisation are obtained with good yields. The same method is also extended for intramolecular Friedel-Crafts alkenylation reactions. Products are obtained quantitatively. A complementary study with chiral allylic acetate and other experiences led to a proposed reaction mechanism.NICE-BU Sciences (060882101) / SudocSudocFranceF

Gravitation and the Universe from large scale-structures: The GAUSS mission concept Mapping the cosmic web up to the reionization era

International audienceToday, thanks in particular to the results of the ESA Planck mission, the concordance cosmological model appears to be the most robust to describe the evolution and content of the Universe from its early to late times. It summarizes the evolution of matter, made mainly of dark matter, from the primordial fluctuations generated by inflation around 10$^{− 30}$ second after the Big Bang to galaxies and clusters of galaxies, 13.8 billion years later, and the evolution of the expansion of space, with a relative slowdown in the matter-dominated era and, since a few billion years, an acceleration powered by dark energy. But we are far from knowing the pillars of this model which are inflation, dark matter and dark energy. Comprehending these fundamental questions requires a detailed mapping of our observable Universe over the whole of cosmic time. The relic radiation provides the starting point and galaxies draw the cosmic web. JAXA’s LiteBIRD mission will map the beginning of our Universe with a crucial test for inflation (its primordial gravity waves), and the ESA Euclid mission will map the most recent half part, crucial for dark energy. The mission concept GAUSS, described in this White Paper, aims at being a mission to fully map the cosmic web up to the reionization era, linking early and late evolution, to tackle and disentangle the crucial degeneracies persisting after the Euclid era between dark matter and inflation properties, dark energy, structure growth and gravitation at large scale

Early Release Science of the exoplanet WASP-39b with JWST NIRCam

International audienceMeasuring the metallicity and carbon-to-oxygen (C/O) ratio in exoplanet atmospheres is a fundamental step towards constraining the dominant chemical processes at work and, if in equilibrium, revealing planet formation histories. Transmission spectroscopy (for example, refs. 1,2) provides the necessary means by constraining the abundances of oxygen- and carbon-bearing species; however, this requires broad wavelength coverage, moderate spectral resolution and high precision, which, together, are not achievable with previous observatories. Now that JWST has commenced science operations, we are able to observe exoplanets at previously uncharted wavelengths and spectral resolutions. Here we report time-series observations of the transiting exoplanet WASP-39b using JWST’s Near InfraRed Camera (NIRCam). The long-wavelength spectroscopic and short-wavelength photometric light curves span 2.0–4.0 micrometres, exhibit minimal systematics and reveal well defined molecular absorption features in the planet’s spectrum. Specifically, we detect gaseous water in the atmosphere and place an upper limit on the abundance of methane. The otherwise prominent carbon dioxide feature at 2.8 micrometres is largely masked by water. The best-fit chemical equilibrium models favour an atmospheric metallicity of 1–100-times solar (that is, an enrichment of elements heavier than helium relative to the Sun) and a substellar C/O ratio. The inferred high metallicity and low C/O ratio may indicate significant accretion of solid materials during planet formation (for example, refs. 3,4,) or disequilibrium processes in the upper atmosphere (for example, refs. 5,6)

Early Release Science of the exoplanet WASP-39b with JWST NIRSpec PRISM

International audienceTransmission spectroscopy of exoplanets has revealed signatures of water vapour, aerosols and alkali metals in a few dozen exoplanet atmospheres. However, these previous inferences with the Hubble and Spitzer Space Telescopes were hindered by the observations’ relatively narrow wavelength range and spectral resolving power, which precluded the unambiguous identification of other chemical species—in particular the primary carbon-bearing molecules. Here we report a broad-wavelength 0.5–5.5 µm atmospheric transmission spectrum of WASP-39b, a 1,200 K, roughly Saturn-mass, Jupiter-radius exoplanet, measured with the JWST NIRSpec’s PRISM mode as part of the JWST Transiting Exoplanet Community Early Release Science Team Program10–12. We robustly detect several chemical species at high significance, including Na (19σ), H$_2$O (33σ), CO$_2$ (28σ) and CO (7σ). The non-detection of CH$_4$, combined with a strong CO$_2$ feature, favours atmospheric models with a super-solar atmospheric metallicity. An unanticipated absorption feature at 4 µm is best explained by SO$_2$ (2.7σ), which could be a tracer of atmospheric photochemistry. These observations demonstrate JWST’s sensitivity to a rich diversity of exoplanet compositions and chemical processes