RSAA Colloquia / Seminars / Feast-of-Facts: 23 Jun 2026 11:30am; DLT


Rob Wittenmyer

"A reunion of old friends: Giant planets in the Gaia era"

The journey to 6000 exoplanets began with giant planets found via the radial-velocity method. In the three decades since, advancements have made Earth-size planet discoveries commonplace. While much attention is being given to ever-smaller planets, I argue that our forgotten giant friends are due for a renaissance. To find and truly understand Earth-like planets, we must first understand Jupiter-like planets. Evidence from our own Solar system, alongside long-term monitoring of Kepler and TESS systems, supports a growing consensus that cold, outer giant planets are correlated with small, inner rocky worlds. Yet, the exact cause of this correlation, and how the presence or absence of an outer giant dictates the properties of inner planets, remain unknown. Key open questions include: How do the mass, radius, and atmospheric compositions of inner planets vary with a giant companion? And how does an outer giant influence the orbital architecture and multiplicity of these inner worlds? While over 200 cold giant planets have been discovered via radial velocity, their true masses and 3-dimensional architectures remain unconstrained due to the limitations of the technique. Pairing radial velocities with Gaia astrometry offers a solution to unlock these systems, already yielding new revelations for known Jupiter analogs. I present a research program designed to address these critical science gaps, leveraging Australian facility access to the Magellan and Giant Magellan Telescopes. This project, in collaboration with key international partners, promises to deliver unprecedented new understanding of the composition, architectures, and atmospheres of planets orbiting nearby stars using the latest high-precision data from ground and space-based telescopes.