Lane, Kaitlyn T.; Stephan, Alexander P.; Soares-Furtado, Melinda; Stassun, Keivan G.; Yarza, Ricardo. (2026).听.听Astrophysical Journal, 1003(1).听
When a planet gets pulled into its host star, it can leave behind clues that astronomers may be able to detect, such as unusual rotation or changes in the star鈥檚 chemical makeup. This study focused on what happens when rocky planets are swallowed by Sun-like stars and how that process changes the star鈥檚 surface chemistry. The researchers built a model that includes a gradual process in which the planet starts to evaporate as it moves through the star鈥檚 outer layers, which means the star can show signs of contamination even if the planet is mostly destroyed below the visible surface layer where material mixes most easily. Their results suggest that this kind of rocky planet pollution is easiest to detect in stars somewhat more massive than the Sun, especially those between about 1.0 and 1.4 times the Sun鈥檚 mass. They also found that certain elements, including aluminium, calcium, vanadium, and lithium, are especially useful for spotting these events. In some cases, the chemical pattern may even reveal whether a star swallowed one large rocky planet or several smaller ones with the same total mass. The study also suggests that these engulfment events usually unfold over years to about a decade, which could help guide future observations of stars that may currently be in the process of consuming planets.
Figure 1.听Schematic of the engulfment process. The figure shows a zoomed-in illustration (not to scale) of an engulfed planet, depicted with a gray center and brown shell to represent the metallic core and rocky mantle, as it travels through the stellar envelope (from left to right, highlighted by the curved black arrow). As the planet travels through the stellar CZ (in yellow), it is gradually evaporated and slowed down by drag interactions at the shock front (blue curve), causing it to sink deeper into the star over time. Along its path, the planet heats and spins up the surrounding stellar material (marked by the dashed curves) and enriches it with evaporated material (represented by the particles coming off of the planet). Depending on the sizes of the planet and the star, the planet may eventually sink below the CZ boundary into the interior radiative zone of the star, marked by the lower light blue region.