A new study by astronomers at University College London and the University of Warwick suggests that as stars age they may destroy the giant planets that orbit closest to them, a process that could reshape the architecture of many planetary systems and influence the population of exoplanets detectable around evolved stars.
Stars change dramatically over their lifetimes. After spending most of their existence fusing hydrogen in their cores on the main sequence, Sun-like stars expand and brighten as they exhaust core hydrogen and evolve into red giants and later phases. That expansion increases stellar radii and luminosities, drives stronger stellar winds and alters the balance of tidal forces between star and planet. For gas giants in short-period orbits—often called “hot Jupiters” when observed around main-sequence stars—these changes can push the planets into peril. Increased tidal interaction and drag from a star’s extended envelope can drain orbital angular momentum, causing orbits to decay until planets are engulfed or tidally disrupted. Enhanced stellar irradiation and mass loss can also strip atmospheres or destabilize orbits over time.
The UCL and Warwick study frames these processes as a potential explanation for patterns already suggested by exoplanet surveys. Observations have shown a relative scarcity of close-in giant planets around evolved, giant-phase stars compared with main-sequence hosts. If aging stars routinely destroy or remove their nearest giant companions, that outcome would naturally produce fewer detectable close-in giants around older, expanded stars. The study’s conclusions therefore connect theoretical expectations about stellar evolution and tidal physics with the demographic properties of known exoplanet samples.
Beyond producing a simple absence of planets, the engulfment or destruction of giant planets could have a range of observable consequences. Swallowed planets may deposit mass and angular momentum into the outer layers of their hosts, potentially altering surface rotation rates or chemical abundances. Planetary debris created during tidal disruption could produce short-lived dust signatures or infrared excesses. In some scenarios, interactions between expanding stellar envelopes and surviving planets can lead to orbital migration or the collision of smaller bodies, reshaping planetary systems in the later stages of stellar life. The study highlights that the survival or fate of planets depends on a combination of initial orbital separation, planet mass and the detailed evolution of the host star.
The finding has implications for interpreting current and future surveys of exoplanets. If aging stars do eliminate their closest giant companions, then counts of surviving planets need to account for post-main-sequence evolution when comparing populations around stars of different ages. That has bearing on attempts to reconstruct planetary formation histories and on estimates of how frequently certain kinds of planets persist over billions of years. The result also informs theoretical models that predict the long-term dynamical stability of planetary systems and the eventual destinies of particular planets as their stars evolve.
Testing the hypothesis will require additional modelling and targeted observations. Detailed simulations of tidal dissipation, stellar expansion and mass loss can refine the predicted thresholds at which planets are lost, while surveys of evolved stars can search for the signatures expected from recent engulfment events, such as anomalous surface chemistry, rotational peculiarities or infrared emission from circumstellar dust. Observations across a range of stellar masses and evolutionary stages will help determine how universal the process is and how it scales with different stellar and planetary properties.
By linking stellar aging with planetary survival, the UCL and Warwick study adds a temporal dimension to understanding exoplanet demographics: the planets we see today may be only a transient snapshot in a longer story of formation, migration and eventual destruction. The research underscores that the present arrangement of a planetary system can be fundamentally altered by its host star’s later life, a consideration that will shape future efforts to map the lifecycles of planets across the galaxy.