Talks

Motivated by the exciting prospect of a new wealth of information arising from the first observations of gravitational and electromagnetic radiation from the same astrophysical phenomena, the Dark Energy Survey (DES) has established a search and discovery program for the optical transients associated with LIGO/Virgo events using the Dark Energy Camera (DECam). This talk presents the discovery of the optical transient associated with the neutron star merger GW170817 using DECam and discusses its implications for the emerging field of multi-messenger cosmology with gravitational waves and optical data.

On the eve of Kepler’s launch in 2009, astronomers knew of a few hundred planets orbiting other stars in the Milky Way.  Today, the discoveries spill into the thousands, and the sensitivity boundaries continue to expand. NASA’s Kepler Mission unveiled a galaxy replete with small planets and revealed populations that don’t exist in our own solar system.  The final discovery catalog was delivered in the autumn of 2017 together with the survey completeness and reliability metrics required for studying exoplanet demographics as a function of size, orbital period, and host star properties.  To date, we’ve learned that every late-type star has at least one planet, that terrestrial-sized planets are more common than larger planets within 1 AU, and that the nearest, potentially habitable earth-sized planet is likely within 5 pc.  This knowledge has catalyzed a 30-year roadmap for NASA exoplanet exploration with the ultimate goal being the search for evidence of life beyond the Solar System.  The launch of the Transiting Exoplanet Survey Satellite (TESS) this year and the James Webb Space Telescope (JWST) in 2019 will take us one step closer.  As our collective effort shifts from Kepler to these new capabilities, the coming decade will shift from exoplanet demographics to exoplanet atmospheres. The community has defined the first exoplanets that will be studied with JWST and is actively preparing for open Data Challenges to enable the best science possible with these new instruments.  Although JWST is not designed as a life finder, it is a means of exercising analysis and modeling tools while stretching our understanding of planetary habitability while NASA teams work on next generation flagship missions.

I warmly thank the organizers of the SAB meeting for inviting me to represent France and our national society, the “Société Française d’Astronomie et d’Astrophysique” (SF2A). SF2A gathers several hundred researchers concerned by astronomy in France. Our society meets every year in a different city in France. Next July, just before the SAB meeting, we will do so in Bordeaux, for the 40 th birthday of SF2A. I will present our society and share with you some of the highlights of our Bordeaux “journées”. During our meeting, we have planed several presentations and workshops concerning the recent discovery of gravitational waves opening a new window on the sky for astronomers. French contributions to large projects are being actively discussed and we expect vigorous exchanges on those too, especially SKA. A series of workshop on large surveys for Galactic and extra-galactic astronomy will also take place in Bordeaux. I will take some time to expose their implications since the evolution of galaxies is a subject close to my heart. On a personal note, I look forward to the progresses we shall make concerning low surface brightness galaxies, such as Malin-1, or recently discovered Ultra Diffuse Galaxies, amazing and still mysterious objects. Finally, I will wonder about the role of our respective societies. SF2A encourages the development and diffusion of astronomy in France, awards prices to young researchers and for PhDs. We maintain relationships with the European society (EAS) and the International Astronomical Union (IAU). We also meet regularly with sister societies all around the globe (making this presentation and visit especially adequate). In the recent years, the council of SF2A has also been concerned by societal issues such as gender problems, the future of young astronomy doctors, the seemingly new rise of obscurantism and the relegation of science to “just another opinion”. What can we do, as scientific societies, or as scientists, on these subjects? I do not have the answer, but we should probably think about it.

This lecture reviews the creep tide theory, a first-principles hydrodynamical theory where the dynamical tide is assimilated to a low-Reynolds-number flow and determined using a Newtonian creep law. The first versions of the theory (AAS/DDA 2012, 2014) were restricted to homogeneous bodies. Recent versions consider the layered structure of stiff bodies (Folonier et al. DPS 2015) and include also the angular momentum leakage in active stars hosting massive companions. The solutions show different behaviors in the two extreme cases. In the case of low-viscosity bodies (high relaxation factor), as close-in gaseous planets and stars, the results are nearly the same as obtained with Darwin’s theory. In the case of close-in planetary satellites and Earth-like planets (low relaxation factor), the results are structurally different. The rotation is damped to periodic attractors nearly commensurable with the orbital period (frequency ratios 1/2, 1, 3/2, 2, 5/2, …), but the final solutions are not stationary even when no permanent triaxiality exists. The resulting oscillations affect the evolution of the systems and the dissipation laws depart from the classical models. The theory was applied to many different bodies as the Moon, Mercury, super-Earths and hot Jupiters and the Saturnian satellites whose oscillations were determined from Cassini’s observations.

The Apache Point Observatory Galactic Evolution Experiment (APOGEE) is an H-band high-resolution spectroscopic survey (R~22,400 from 1.5-1.7um) of hundreds of thousands of stars from all Galactic populations. An automated analysis derives stellar parameters and detailed chemical abundance distributions based on synthetic spectral libraries computed using the APOGEE spectral line list. The infrared (IR) spectral region at wavelengths from ~1-5um will play an increasingly important role in future large spectroscopic surveys. This region is ideal for using red giants to probe chemical evolution of the Galaxy throughout its entire volume, including the inner bulge, bar, or Galactic center, as dust extinction is much lower in the IR when compared to the optical. We will highlight recent science results from APOGEE, with emphasis on chemical evolution and stellar age maps across the Galaxy, along with detailed discussions of internal red giant nucleosynthesis and mixing.

We are born curious. Our exploration of the universe begins almost the moment we are born and expands as we grow. How to we support and encourage that exploration at every stage and for everybody, beyond those who are currently thriving in our field? Discover ways that innovative educators are increasing the capacity of our astronomy pipeline and redefining what it means to be a scientist in the 21st century.