Subgiant star TOI-5882’s lithium excess hints at planet engulfment

TOI-5882 is a subgiant star that stands out for its unusually high lithium content. The star also hosts a massive brown dwarf companion, which can disturb the orbits of any inner planets. Theoretical models suggest that subgiant stars in a certain mass range can retain lithium signatures if they have recently swallowed a planet. To test this, researchers measured the lithium abundance in TOI-5882 using high-resolution spectra and compared it to a control group of similar subgiants. They found that TOI-5882 is in the top 2 percent for lithium content among its peers, confirming significant enrichment.

Star system: TOI-5882 A | Distance from the Sun: 1367 light years

The team modeled how much planetary material would need to be engulfed to explain the observed lithium. Their calculations show that the required mass is consistent with the ingestion of a planet between the size of a super-Earth and Neptune, especially if the planet was rich in heavy elements. This is much less than what would be needed if the planet had a composition similar to the Sun. The presence of the brown dwarf companion makes it likely that inner planets could have been perturbed and eventually swallowed by the star.

These findings support the idea that TOI-5882’s lithium excess is the result of a recent planetary engulfment event. The study encourages further research to confirm this scenario and to better understand how such events affect the evolution of stars and their planetary systems.

Key findings
- TOI-5882 is a subgiant star with unusually high lithium abundance.
- The star’s lithium content ranks in the top 2 percent among similar subgiants.
- Modeling suggests the lithium excess could result from engulfing a super-Earth to Neptune-mass planet.
- The brown dwarf companion may have disturbed inner planets, leading to engulfment.
- The study supports planetary ingestion as a cause of lithium enrichment in subgiants.

Scientific study

Lithium Enrichment in a Subgiant Star with a Brown Dwarf Companion: A Planetary Engulfment Candidate (external link)