Exploring the Diversity of Planetary Systems

JWST has transformed the study of exoplanets by obtaining exquisitely precise spectroscopic observations. Although some planets appear to be shrouded by hazes or clouds, JWST has constrained the atmospheric compositions of multiple planets and revealed that several potentially terrestrial worlds are likely to be airless. At larger orbital separations, JWST has achieved new sensitivity levels in directly imaging and obtaining direct spectroscopy of young, massive planets. In 2027, the Roman Space Telescope will further advance studies of distant planets via direct imaging and spectroscopy with the Coronagraphic Instrument, which will be capable of imaging even fainter planets and disks. Roman will also significantly expand knowledge of exoplanet demographics by using gravitational microlensing to detect hundreds of planets with masses as small as that of Mars. Roman’s microlensing detections will be at orbital separations of roughly 0.5 astronomical units and beyond, thereby complementing previous studies of the demographics of close-in planets by radial velocity and transit surveys, especially the NASA Kepler, K2, and TESS missions. From the ground, extremely precise radial velocity spectrographs, sophisticated analysis techniques, and an improved understanding of stellar astrophysics will improve planet mass measurements and ideally lead to precise mass measurements for planets with similar masses, radii, and temperatures as the Earth. Future direct imaging and spectroscopy observations with extremely large ground-based telescopes will probe the atmospheres of small, potentially habitable planets orbiting the coolest stars and search for signs of life. From space, the upcoming Habitable Worlds Observatory (HWO), a large aperture telescope with sensitivity from the UV to the NIR, will conduct transformative studies in general astrophysics and search for signs of life by directly imaging and obtaining spectra of roughly 25 habitable zone planets orbiting Sun-like stars. The observatory will also obtain near-flyby quality observations of solar system objects and observe hundreds of exoplanets with a range of masses, radii, atmospheric compositions, and orbital properties.