Avec l’arrivée des données complexes et multi-variées de la mission spatiale Gaia et des grands relevés complémentaires au sol, les outils d’interprétation que sont les modèles ont besoin d’être adaptés et renforcés. Le modèle de la Galaxie de Besançon est un modèle qui utilise la synthèse de populations stellaires pour tenter d’expliquer les observations de tous types (photométrie, spectroscopie, astrométrie) et dans un grand intervalle de longueur d’onde (de l’UV jusqu’à l’infrarouge moyen), en se basant sur des hypothèses réalistes de formation et d’évolution de la Galaxie. Il prend en compte les derniers modèles d’évolution stellaire, la matière interstellaire, la distribution de la matière noire. Je passerai en revue les derniers avancements dans le développement du modèle, les résultats récents en terme d’évolution de la Galaxie et les perspectives avec l’arrivée des données de la mission Gaia.
To date, ten circumbinary planets orbiting around a close main sequence binary have beed detected by the Kepler space mission. Most of these planets are located just outside the limit of dynamical stability, in a region where gravitational perturbations from the central binary make their in-situ formation very challenging. This suggests that circumbinary planets may have formed further out in the disc and moved to their current positions by disc-driven migration. In the context of this scenario, the orbital configuration of circumbinary planets is determined through the interaction with the circumbinary disc, which develops an inner cavity and becomes eccentric due to the interaction with the central binary. Understanding what physics shape the disc structure is therefore a crucial issue to explain the current orbital architecture of the Kepler circumbinary planets. To this aim, I will present the results of a recent study that investigates the impact of self-gravity on the evolution and structure of circumbinary discs, as well as the evolution of planets in these discs. I will also discuss the effect of disc warping that arises when the disc and orbital plane of the central binary are slightly misaligned.
Detecting and studying the magnetic fields of exoplanets will allow for the investigation of their interior structure, rotation period, atmospheric dynamics and escape, moons, and potential habitability. It was postulated that the magnetic fields of short-period exoplanets could be constrained if their near-UV light curves start earlier than in their optical light curves. This effect can be explained by the presence of a bow shock in front of the planet formed by interactions between the stellar coronal material and the planet’s magnetosphere. Furthermore, if the shocked material in the magnetosheath is optically thick, it will absorb starlight and cause an early ingress in the near-UV light curve. We observed the transits of 19 short-period exoplanets from the ground in the near-UV. All of our observations resulted in non-detections of the desired effect but we can still put constraints on the planetary atmospheres with our data. To explain our non-detections we simulate the atomic physics, chemistry, radiation transport, and dynamics of the plasma characteristics in the vicinity of short-period exoplanets using the code CLOUDY. Using CLOUDY we have investigated whether there is an absorption species in the near-UV that can exist to cause an observable early ingress. We find that there isn’t a species in any wavelength (including near-UV) that can cause an absorption. Therefore, we show though observations and theory that the near-UV transit method for detecting exoplanet magnetic fields needs to be updated. Additionally, we also simulate escaping planetary gas in ionization and thermal equilibrium with the stellar radiation field with CLOUDY Promising sources of opacity from the X-ray to radio wavelengths are found, some of which are not yet observed.
ROSETTA space mission, launched on March 2004, for the comet Churyumov-Gerasimenko (67P / C-G) was composed of an orbiter and Philae lander. The payload contained multiple instruments performing the teledetection and in situe measurements. The probe was accompanying the comet on its journey around the sun on the orbits close to the nucleus on the distance from tens to hundreds kilometers. The scientific objective of the mission is the study the cometary material, the surface and the internal structure of the comet and their evolution on the their journey around the sun.
The main scientific questions are:
How have formed and evolved comets? What are the physical propreties, structure of surface and interior of comets? What is the composition of the ice grains, molecules, organic? Have they played a role in the evolution of the planets?
On 12 November 2014 Philae lander, after some twists and turns, landed on the surface of the comet. This was a spectacular success and the first cometary landing in the history of the exploration of the solar system.
In our presentation we will describe the payloads of the probe and of Philae. We present and discuss some scientific results by ROSETTA and also by Philae.
We describe more specifically CONSERT bistatic radar, which the primary scientific goal was to investigate the deep interior of the nucleus of the comet. The radar had operated between the Rosetta spacecraft and Philae lander and through radio tomographic mapping between the lander and the main spacecraft, obtained important scientific results about the internal structure and composition of the comet 67/P C-G.
The Origins Space Telescope is one of the four flagship missions currently under study for the 2020 US decadal survey. OST will cover the full infrared wavelength domain, from 6.5 to about 500 microns. The science goals and associated measurement requirements for OST are being established by a
community-based Science and Technology Definition Team (STDT). The STDT is supported by a NASA
Center Study Office based at NASA’s Goddard Space Flight Center, with partners at several other
NASA Centers and industry teams.
I will present the first mission concept, a cooled 9m telescope equipped with five instruments enabling sensitive imaging, spectroscopy and polarimetry to answer compelling questions in astrophysics such as the origin of black holes and galaxies, the origins of elements, the trail of water from the cold ISM to
disks and planets, etc.
This talk will present the OST study and describe the french participation supported by CNES.