This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: An international team led by researchers from the University of São Paulo (USP) in Brazil has developed an innovative method to identify stars that have consumed the planets around them. The technique detects variations in the abundance of beryllium, a relatively rare chemical element, and could open a new window into studying the evolution of planetary systems.
The study, published in the journal Astronomy & Astrophysics, analyzed a binary system consisting of two very similar solar-type stars (with physical, chemical and magnetic activity characteristics similar to those of our sun), named HD 129171 and HD 129209. In principle, binary stars like these should have virtually the same chemical composition because they formed from the same molecular cloud (a cluster of dust and gas that acts as a stellar nursery). However, the researchers found significant differences between the two stars.
"The star HD 129171 is enriched in refractory elements—that is, elements that typically condense in the solid state and make up rocky planets. That strongly suggests that it has engulfed planetary material throughout its evolution," says Anne Rathsam, a doctoral student at the Institute of Astronomy, Geophysics and Atmospheric Sciences (IAG-USP) and the first author of the article. Scientists had previously suspected that some stars might incorporate planets or planetary fragments.
This new study is unique because it demonstrated for the first time that differences in beryllium abundance in binary stars can reliably indicate this process. Beryllium has an important characteristic: It is not produced in the "heart" of stars throughout their evolution. Therefore, when astronomers detect the signature of this element in the light emitted by a star, it is a warning sign.
This indicates that the star swallowed rocky material, such as planetary remnants, long after forming. As the authors explain, lithium, beryllium and boron are important exceptions in the chemical history of the universe. "All other chemical elements originate from primordial nucleosynthesis [the formation of the first atomic nuclei in the minutes following the Big Bang] or stellar nucleosynthesis [the nuclear fusion process that occurs inside stars throughout their lifetimes].
But not beryllium and boron. They primarily arise through a process called 'cosmic spallation,' in which high-energy particles fragment heavier nuclei, such as carbon, nitrogen and oxygen, producing lighter elements," explains Jorge Luis Melendez Moreno, an astronomer and professor at IAG-USP, as well as the study adviser. Lithium is also produced primarily by spallation, although a minuscule amount of this element arose during primordial nucleosynthesis, and it can form in certain types of stars under special circumstances.
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