Chemical differences in binary star pair suggest planetary engulfment

Star system: HD 129171 | Distance from the Sun: 179 light years

Stars born from the same cloud in a binary system are generally expected to have identical chemical compositions. However, some binary systems exhibit unexplained chemical differences, leading researchers to debate whether these anomalies originate from their birth environment or are the result of external events. This study examines the binary pair HD 129171 and HD 129209, which show significant differences in their abundances of iron, lithium, and other elements.

To investigate these differences, researchers used high-resolution spectra gathered by the UVES instrument to conduct a detailed analysis of the stars' chemical compositions. They particularly focused on the abundance of beryllium, which serves as a powerful diagnostic tool for identifying past ingestion events of rocky material in solar-type stars. By comparing their findings with models of planetary engulfment, the team explored whether one of the stars had consumed a planet.

The analysis confirmed significant discrepancies in the levels of iron, lithium, and beryllium between the two stars. The observed chemical pattern is well-reproduced by a model in which one of the stars engulfed approximately 11.2 Earth masses of rocky material. This discovery provides strong evidence that planetary engulfment can cause detectable chemical changes in binary star systems. Furthermore, it suggests that measuring beryllium differences can be a highly effective way to identify similar ingestion events in other chemically unusual binary pairs.

Key findings
- The binary pair HD 129171 and HD 129209 shows significant differences in iron, lithium, and beryllium abundances.
- Researchers modeled the chemical pattern and found it consistent with the ingestion of 11.2 Earth masses of rocky material by one of the stars.
- These results support the hypothesis that planetary engulfment events are responsible for certain chemical anomalies in binary systems.
- Beryllium abundance differences act as a reliable diagnostic tool for identifying rocky material ingestion in solar-type stars.

Scientific study

Planet engulfment in the chemically anomalous HD 129171/HD 129209 pair (external link)