LAM Seminars

Magnetometric measurements carried out by the Galileo mission
(1996-2003) revealed that Jupiter’s three large icy moons (Europa,
Ganymede, Callisto) likely harbor a subsurface salty ocean underneath
their cold icy surface. However, the depth and composition of these
internal oceans still remains poorly constrained. ESA’s JUICE and
NASA’s Europa Clipper missions are currently en route to Jupiter with
the primary objective to characterize these subsurface oceans and
assess their habitability potential. Both spacecrafts are equipped by
a complementary suite of geophysical, remote sensing and in situ
instruments which will provide unique data of unprecedented accuracy
on the moons’ interior, surface, exosphere and interaction with
Jupiter’s environment. In this seminar, after reviewing the current
knowledge on these ice-covered ocean worlds, I present how synergies
between the different instruments on both spacecrafts, supported by
numerical modeling and experimental data, will allow us to determine
the structure, dynamics and composition of these oceans, essential for
assessing the astrobiological potential of these oceanic environments.

Short bio:
G. Tobie is planetary scientist at CNRS (LPG, Nantes), expert in the
study of icy worlds. He is associated with ESA’s JUICE as co-I on the
gravity experiment, 3GM, and team member of the spectra-imager MAJIS,
and co-lead of the WG1 Interiors/Geophysics. He is also co-I on the
dust analyzer SUDA onboard NASA’s Europa Clipper.

Jupiter’s radio emissions have been intensively studied since their discovery some 70 years ago. Space missions have extended these studies to radio emissions from all planetary magnetospheres in the solar system. Main emission characteristics have been determined and their generation process elucidated. The 3 magnetospheric engines of these emissions are now well documented (solar wind-magnetosphere, magnetosphere-ionosphere, and satellite-planet interactions). On that basis, we can extrapolate our knowledge to star-exoplanet systems, and attempt to detect radio emissions from these systems. Motivations include direct exoplanetary magnetic field measurement, planetary protection, compared magnetospheric physics and exo-space weather. I will give an overview of the theoretical framework and observational results to date, with prospects for the coming years.

Philippe Zarka, Paris Observatory – CNRS – PSL, France
philippe.zarka@obspm.fr, http://www.lesia.obspm.fr/perso/philippe-zarka/, orcid.org/0000-0003-1672-9878

Antonio de Ugarte Postigo, OCA

GRBs in the SVOM era: Observations and instrumentation

Progress and surprises in studies of early galaxies with JWST

Richard Ellis, University College London

Abstract: I will attempt to briefly review the astonishing progress made in studies of early galaxies during the first two years of JWST science operations. Although redshift frontiers have been extended beyond those reached with HST and large ground-based telescopes, it is the superb quality of the new data, particularly in the near and mid infrared spectral regions, that represents the primary advance. Spectroscopically, JWST has transformed the observational landscape by measuring the chemical composition of interstellar gas to redshifts beyond z=10 and identifying likely signatures of early and hitherto unrecognised active galactic nuclei. Its superlative image quality is also advantageous, enabling studies of resolved kinematics and stellar populations in distant galaxies. As a result we can now address long-standing questions including which sources likely governed cosmic reionisation, the origin of supermassive black holes, and the role that dust may play in obscuring our census of early systems. We are also tempted to consider whether JWST can locate “cosmic dawn” when chemically-pristine galaxies first emerged from darkness. In addition to discussing JWST’s numerous achievements in the context of these questions, I will also mention some surprises that may, in turn, lead to unforeseen discoveries.

The seminar will start at 11am.

Galactic dynamics in the Gaia era

Benoit Famaey, Observatoire astronomique de Strasbourg

I briefly present some basic tools of theoretical Galactic dynamics, both in terms of the construction of equilibrium models and of linear perturbation theory. Then, I show how we can construct a stellar phase-space distribution function in the joint presence of the Galactic bar and spiral arms, which matches the exquisite data from Gaia. This provides for the first time a purely dynamical map of the non-axisymmetric structure of our Galaxy.