Archives Séminaires 2020-2021

Séminaire IPAG de Eleonora Bianchi (IPAG), jeudi 25 mars 2021, 11h00, IPAG seminar room

How the chemical complexity evolves during the process leading to the formation of a Sun and its planetary system ? Is the chemical richness of a Solar-like planetary system partially inherited from the earliest stages or there is a complete chemical reset ? Recent evidence suggests that planet formation probably starts already in young protostellar disks (Class I stage 105 yr). Therefore, studing their chemical compositions represents a key step in our understanding of the initial (...)

Séminaire IPAG de Florian Debras (IRAP), jeudi 1 avril 2021, 11h00, IPAG seminar room

More than 4000 exoplanets have been discovered in the last decade and the number of known exoplanets will increase significantly in the coming years, especially with the TESS satellite. We now have access to many statistics on the mass-radius diagram of planets, the distribution according to stellar type or the average number of planets per star. However, for the same density, two planets can have very different physical characteristics. Current research on exoplanets is therefore directed (...)

Séminaire IPAG de Anaëlle Maury (CEA Saclay), jeudi 8 avril 2021, 11h00, IPAG seminar room

Understanding the first steps in the formation of stars and protoplanetary disks is a great unsolved problem of modern astrophysics. The key to make progress on this topic is to confront theoretical models and high-resolution studies of the youngest protostars, observed less than 0.1 Myrs after the onset of protostellar formation. I will present some investigations of solar-type Class 0 protostars that we carried out in the framework of the [CALYPSO->http://irfu.cea.fr/Projets/Calypso and (...)

Séminaire IPAG de Gaylor Wafflard (IPAG), jeudi 15 avril 2021, 11h00, IPAG seminar room

Recent observations of spatially resolved protoplanetary disks, in particular with the radio interferometer ALMA, reveal a large diversity of substructures in the dust thermal emission (sequences of dark rings (gaps) and bright rings, asymmetries, spirals, ...). A key challenge for protoplanetary disks and planet formation models is to be able to make a reliable connection between these observed substructures and the supposed existence of planets impacting the dust content of protoplanetary (...)

Séminaire IPAG de Anna Grassi (LULI), jeudi 29 avril 2021, 11h00, IPAG seminar room

Collisionless shocks are ubiquitous in astrophysical plasmas and play an important role in magnetic field generation/amplification and particle acceleration. While diffusive shock acceleration (DSA) is well established, the details of particle injection into DSA remain a long-standing puzzle, particularly for electrons. High-energy-density (HED) plasma experiments and kinetic plasma simulations offer a promising route to identify the dominant processes at play. Very recently experiments (...)

Séminaire IPAG de Romane Le Gal (IRAP), jeudi 6 mai 2021, 11h00, IPAG seminar room

Over the past decades, questions about the origins and prevalence of life on planets have shifted from metaphysical questions to hot research topics in astrophysics. The latest generation of high-sensitivity telescopes (ALMA, NOEMA, SPHERE, JWST) is providing access to the cradles of star and planet formation at unprecedented spatial and spectral resolutions, making it possible to study the chemical evolution of interstellar matter from molecular clouds to forming planetary systems. In (...)

Séminaire IPAG de Olivier Le Contel (LPP), jeudi 20 mai 2021, 11h00, IPAG seminar room

The MMS (Magnetospheric Multi-Scale) mission was launched on March 12th 2015 by an Atlas V rocket from Cape Canaveral, Florida. Like the European Cluster mission, MMS consists of four identically instrumented spacecraft which measure particles, electric and magnetic fields in the Earth’s magnetized environment. However, while the Cluster mission has mainly investigated the plasma processes at the fluid and ion scale, MMS was designed to address these processes at the electron dynamics scale. (...)

Séminaire IPAG de Pascal Tremblin (CEA/MdS), jeudi 27 mai 2021, 11h00, IPAG seminar room

We present a new conservative finite volume numerical scheme for the study of stratified hydrodynamics that is able to capture both low-Mach and high-Mach flows (all-regime) and hydrostatic equilibrium at machine precision (well-balanced). The scheme is based on a splitting strategy between the acoustic and transport part of the Euler system and can be implemented in a implicit-explicit approach to get rid of the restrictive sound-speed CFL condition while being fully conservative. This new (...)

Séminaire IPAG de Benoît Tabone (Leiden), jeudi 3 juin 2021, 11h00, IPAG seminar room

The physical evolution of disks around nascent stars controls the final architecture of planetary systems. Over the past decade, the paradigm of "viscous disks" that explains disk accretion by turbulence and disk dispersal by photoevaporative winds has been challenged. The launching of a magnetized wind from the disk surface (’’MHD disk-winds’’) is often proposed as a compelling scenario to account for disk accretion but remains largely unconstrained.

In this seminar, I will present our (...)

Séminaire IPAG de Fabien Casse (APC), jeudi 10 juin 2021, 11h00, IPAG seminar room

Over the last century, the existence of black holes in the Universe has slowly shifted from a mere mathematical solution of Einstein equations into a likely driver of some of the most powerful astrophysical sytems in the Universe. Very recent observations from the Gravity collaboration or from the Event Horizon Telescope has provided unprecedent pictures of the effect of the strong gravity of black hole upon matter orbiting in their close vicinity. The final proof of the existence of black (...)