Fakultät für Physik und Astronomie
STEPHEN PHILLIPS hostreviews.co.uk / UNSPLASH

The outer reaches of extrasolar systems: exoplanets, brown dwarfs and debris disks with high-contrast imaging

Elisabeth Matthews , MPIA

Direct detection of exoplanets is challenging: there is an enormous contrast barrier and a small angular separation between a star and any planets that are in orbit\; these planets are also rare, and blind surveys for these objects are expensive. However, once detected, imaged planets can provide a wealth of information about the planet atmosphere through detailed photometric and spectroscopic campaigns. To date, only a small handful of exoplanets have been directly detected, and the population consists primarily of young, hot planets which are still re-radiating their formation energy - with very little overlap with the population of indirectly detected planets. However, cold faint planets are some of the most fascinating: they are the most similar to those in our own solar system, providing context for the study of Jupiter and observationally calibrating theoretical evolution models as the planets approach equilibrium temperature. Their atmospheric chemistry is expected to be dominated by molecules such as CH4, H2O and NH3, and water clouds are also predicted. The unprecedented sensitivity of the James Webb Space Telescope allows access to this cold population of exoplanets for the first time — yet selecting appropriate targets for deep imaging campaigns is critical.

In this talk I will highlight our efforts to use ancillary information to target direct imaging campaigns and image cool planets. Radial velocity campaigns, astrometric accelerations, and debris disk signatures can all provide clues as to the best targets to image. Planets in these systems are particularly amenable to detailed characterization: for example, imaging planets in systems with debris disks allows a detailed study of the disk-planet interactions. Imaging planets with RV information allow us to simultaneously measure precise dynamical masses, bolometric luminosities, and atmospheric compositions, and characterize the orbits of these companions, and early measurements challenge evolutionary models. This technique has led to my recent discovery of the cold planet Eps Ind Ac with JWST/MIRI coronagraphic imaging. Eps Ind Ac is the oldest and coldest exoplanet ever directly imaged, and the first confirmed planet discovered with JWST imaging. Early comparison to models indicates a clear tension with both atmospheric and evolutionary models for solar-age exoplanets, but the bright flux and wide separation make this source ideally suited to future characterization efforts that may shed light on this tension.

Königstuhl Colloquium
23 Feb 2024, 11:00
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)

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