Archives Séminaires 2020-2021

Séminaire IPAG de Thierry Dudok de Wit (LPC2E Orléans), jeudi 7 janvier 2021, 11h00, IPAG seminar room

Parker Solar Probe, which was launched in 2018, is the first spacecraft to literally enter a stellar atmosphere. This NASA mission will ultimately come within 8.8 solar radii (0.04 AU) of the solar surface. The primary objective of Parker Solar Probe is to understand the mechanisms that generate the solar wind and cause solar and stellar atmospheres to be so much hotter than the surface. To do so it measures in situ properties of waves and particles, but also has an imager to view the (…)

Séminaire IPAG de Ileyk El Mellah (IPAG), jeudi 14 janvier 2021, 11h00, IPAG seminar room

Once stars leave the main sequence, their evolution is largely set by mass loss through dust-driven or radiation-driven winds for cool and hot stars respectively. An illustration of the former is given by low and intermediate mass stars on the asymptotic and red giant branch, while a typical example of the latter are blue supergiants and Wolf-Rayet stars. Stellar multiplicity has been recognized as a ubiquitous feature : stars seldom live an effectively single life. In the advanced (…)

Séminaire IPAG de Benjamin Tessore (IPAG), jeudi 21 janvier 2021, 11h00, IPAG seminar room

In this talk I will present MCFOST-ART, a code dedicated to the modelling of atomic emission lines formed in the environment of stars. The code is flexible, versatile, and has been designed to work with MHD simulations considering the coupling between the gas and dust. I will place particular emphasis on the hydrogen lines emission coming from the magnetosphere of T Tauri stars.
Radiation plays a key role in many aspects of the evolution of young stars. The modelling of the spectral (…)

Séminaire IPAG de François Mernier (ESA ESTEC), jeudi 28 janvier 2021, 11h00, IPAG seminar room

Despite being the building blocks of rocky planets and even life, metals mostly reside outside galaxies - i.e. within a hot, ionized, X-ray emitting plasma pervading galaxy clusters and groups, and massive ellipticals. The presence of these metals in such volumes constitutes thus a fossil record of the enrichment of the largest-scale structures of our Universe, and measuring the abundance of their chemical elements (via X-ray spectroscopy) in these systems is the key to understand when, (…)

Séminaire IPAG de Guillaume Laibe (CRAL), jeudi 4 février 2021, 11h00, IPAG seminar room

Les planètes se sont-elles formées plus tôt que ce que suggère le scénario classique de la nébuleuse planétaire ? Si oui, les solides issus du milieu interstellaire doivent grossir de manière extrêmement efficace afin de former les embryons des coeurs planétaires. Je présenterai des mécanismes - plus ou moins efficaces - pour concentrer ces grains dans les objets stellaires (très) jeunes.
Did planets form earlier than the classic scenario of the planetary nebula suggests ? If so, solids (…)

Séminaire IPAG de Yun Zhang (Lagrange), jeudi 11 février 2021, 11h00, IPAG seminar room

Most small bodies with sizes larger than tens of meters are made of numerous pieces of rocks and sometimes ices that have coalesced under the influence of gravity (so called “rubble piles”). As their own gravity is not enough to squeeze them into spheres, these small bodies exhibit a variety of shapes and surface morphologies, recording their life stories. Here I will show by numerical simulations how small bodies are reshaped in general subject to various effects, e.g., collisions, solar (…)

Séminaire IPAG de Pierre Marchand (American Museum of Natural History), jeudi 25 février 2021, 15h, IPAG seminar room

Le séminaire aura lieu exceptionnellement à 15h // The seminar will take place exceptionally at 3pm
Magnetic fields play an important role during the protostellar collapse, through the magnetic braking and outflows. Non-ideal MHD effects decouple the field and the gas, with a major influence on these processes. The strength of the non-ideal MHD effects depend on the abundance and nature of the charged particles ; it is therefore crucial to know with precision the number and electric charge (…)

Séminaire IPAG de Clément Robert (IPAG), jeudi 4 mars 2021, 11h00, IPAG seminar room

Lopsided structures are resolved in the thermal emission of a handful of circumstellar disks, tracing azimuthal concentration of solids, forming "clumps". One mechanism to create such dusty clumps is provided by anti-cyclonic vortices, whose formation is also expected on sharp "edges" of cavities and planet-carved gaps (via the Rossby Wave Instability). However, correctly classifying known targets as actual vortices (as opposed to other possible dust-accumulating scenarios) requires more (…)

Séminaire IPAG de Frédéric Bournaud (CEA Saclay), jeudi 11 mars 2021, 11h00, IPAG seminar room

Cosmological simulations of galaxy formation are reaching a high level of accuracy and can finely reproduce some of the main properties of galaxy populations : stellar masses, angular momentum, colors, etc. However, most galaxy formation simulations still fail to account for the detailed structure of galaxies and their global star formation history. Using high-resolution, idealized simulations of galactic dynamics and star formation, I will show that these disagreements are not cosmetic (…)

Séminaire IPAG de Christophe Lovis (Université de Genève), jeudi 18 mars 2021, 11h00, IPAG seminar room

RISTRETTO will be a novel high-resolution spectrograph fed by a high-performance adaptive optics system at the VLT. It will offer high spatial and spectral resolution in the visible, enabling new exoplanet and solar system science. The main science goal of RISTRETTO is reflected-light spectroscopy of exoplanets orbiting very nearby stars, among which Proxima b. A number of exoplanets of various sizes and irradiation levels will be amenable to atmospheric and surface characterization, opening (…)