Beryllium excess in sun-like star reveals it engulfed rocky planets

By the Everything Space news desk · 09 Sep 2026 · written from the sources below

Image: Phys.org

A binary star study suggests planet-swallowing may be common, raising questions about how rare stable systems like ours truly are.

Astronomers led by a team at the University of São Paulo have identified a new chemical signature that reveals when a star has consumed one of its own planets: unusually high levels of beryllium. The finding, based on a detailed study of a binary star pair, offers a more reliable tool than previously used methods for detecting planetary engulfment.

The researchers examined two sun-like stars, HD 129171 and HD 129209, which formed together from the same cloud of gas and dust and should therefore share nearly identical chemistry. Instead, one of the pair, HD 129171, showed a marked excess of elements common in rocky planets, along with elevated beryllium and lithium, pointing to the absorption of planetary material equivalent to more than 11 Earth masses.

Unlike most elements, beryllium is not created inside stars through nuclear fusion but instead forms when high-energy particles break apart heavier atoms in a process called cosmic spallation. Because stars don't manufacture it internally, any beryllium detected in a star's light signals that the material came from an external source, such as a swallowed planet or planetary debris. Researchers note beryllium persists longer than lithium, which is easily destroyed, making it a more durable marker of past engulfment.

The team used the UVES spectrograph on the European Southern Observatory's Very Large Telescope in Chile to tease out these subtle chemical differences. They say the excess material likely came either from a single large planet or several smaller bodies, though the internal mixing in sun-like stars makes it impossible to pin down which scenario occurred.

Beyond identifying a new detection method, the study feeds into a broader debate about how common stable planetary systems like our own solar system actually are. Combined with simulations of planet formation and surveys showing few Jupiter-like planets in orbits similar to Jupiter's, the results suggest that calm, long-term stable systems may be the exception rather than the rule, with many systems instead undergoing disruptive phases that fling or swallow planets.

Researchers involved in the study suggest this instability could have consequences for the emergence of complex life, which may require not just enough time to evolve but also a planet remaining in a steady orbit undisturbed by major gravitational upheaval.

Because roughly half of the stars in the Milky Way exist in binary or multiple systems that form from the same original material, comparing companion stars like these offers a rare way to detect chemical changes caused by planet consumption long after formation, with implications for how scientists reconstruct the chemical history of the galaxy.

Written in Everything Space’s own words by our news-desk model from the sources above, and checked against them in code: every number in this report appears in its sources, and no sentence is copied from them.