Astronomers have identified chemical anomalies between a pair of binary stars that strongly suggest one of them has devoured at least one exoplanet. The twin stars, born from the same molecular cloud and expected to share identical compositions, instead show distinct chemical signatures in their atmospheres. This finding provides direct observational evidence of planetary engulfment by a host star, a process long theorized but rarely observed so clearly.
The discovery hinges on spectroscopic analysis that revealed an excess of certain elements — particularly iron and other refractory metals — in the atmosphere of one star compared to its sibling. Such an enrichment pattern is consistent with the ingestion of rocky planetary material. The researchers note that the devoured planet likely had a mass similar to one of the solar system's terrestrial worlds, though the exact size remains uncertain.
Binary star systems offer a unique laboratory for such studies because both stars are expected to have the same initial chemical makeup. Any significant deviation points to a later accretion event. In this case, the polluted star's outer layers contain a higher abundance of elements that condense at high temperatures — a fingerprint of planetary material that spiraled into the star.
This observation has implications beyond the fate of exoplanets. It sheds light on how planetary systems ultimately evolve when their host stars age and expand. The engulfment process could also help explain the diversity of exoplanetary systems observed across the galaxy, particularly those with planets that migrate close to their stars before being consumed.
However, some researchers caution that chemical differences could also arise from other processes, such as stellar magnetic activity or mass transfer between the two stars. The team plans further observations to rule out these alternative explanations and to search for additional binary systems with similar anomalies.