TOI-5882 Devours 1 Planet as 22-Jupiter-Mass Brown Dwarf May Be Next

Q: What chemical clues do devoured planets leave in a star's atmosphere, revealing their final moments to astronomers?

The clearest chemical clue is an unusual spike in lithium in the star’s outer atmosphere. In stars like TOI-5882, lithium is normally depleted as the star evolves, so a strong lithium signal stands out as evidence that fresh, lithium-rich planetary material was recently dumped into the star. Astronomers detect that clue through spectroscopy, reading the star’s light for elemental fingerprints. In TOI-5882, the lithium abundance was far higher than expected for a comparable early subgiant, making it a strong sign of planetary engulfment. Researchers describe this as seeing the “half-digested remains” of the lost world in the star’s photosphere. Other abundance anomalies can help refine the picture. Engulfed planets can leave patterns in refractory elements such as magnesium, silicon, iron and calcium, sometimes resembling the chemistry of rocky planets or meteorites. By comparing those ratios with similar stars, astronomers can estimate whether the consumed body was more like a super-Earth, a Neptune-like rocky world, or another type of planet. The reason these clues matter is timing. The engulfment itself may happen quickly, over days or weeks, but the chemical fingerprint can linger briefly in the star’s surface layers before mixing and dilution erase it. That makes lithium, especially, a valuable forensic marker of a planet’s final plunge.

1 articles · Updated · The New York Times · Jul 9

About 1,300 light-years from Earth, TOI-5882 shows chemical traces that it recently swallowed a planet, giving astronomers a fresh example of planetary engulfment in action.
A 22-times-Jupiter-mass brown dwarf orbiting close to the star likely destabilized that planet's orbit and flung it into the star, according to one of two new studies.
The same brown dwarf is also expected to be engulfed by TOI-5882, with a second study suggesting that fate may come sooner than previously thought.
Planetary engulfment helps researchers link stellar chemistry to exoplanet dynamics and offers a preview of processes that could one day consume Mercury, Venus and possibly Earth when the sun becomes a red giant.