Astronomers have discovered some of the strongest evidence to date that stars can swallow their own planets. A new study confirms the long-held belief that young stars are capable of “consuming” nearby worlds as planetary systems form.
Lithium imprint in the chemical composition of stars
Researchers from the University of Cologne and the University of Exeter studied thousands of stars and found evidence that six different red dwarfs—the smallest, coolest, and most common type of star in the universe—have swallowed Earth-like planets.
“What gave it away was a highly distinctive chemical ‘fingerprint,’” said lead author Professor Robin Jeffries of Keele University. “We found that several of the red dwarf stars we studied contained lithium, a chemical element that shouldn’t be there,” he explained.
Professor Robin Jeffries added, “Red dwarfs are smaller and cooler than our sun, but they are extremely hot inside. This heat must destroy all their fragile lithium in nuclear reactions shortly after they form.”
Consequently, it has previously been suggested that the detection of lithium in their atmospheres could indicate the absorption of additional lithium-rich material originating from the surrounding planetary system.
Evidence of planetary accretion
In a new study, scientists examined young star clusters using spectroscopic data to investigate how different materials interact with electromagnetic radiation.
Data from the Gaia-ESO (GES) spectroscopic survey covered thousands of stars, among which the team identified six distinct red dwarfs in three separate clusters that had significantly higher lithium abundances than other stars of the same spectral type.
Analysis of these stars indicates that they dramatically “devoured” their surrounding Earth-like planets—or roughly 3 to 10 Earth masses of planetary material in total—which provided a fresh influx of lithium into their atmospheres, which would otherwise have been very low in lithium.
These accretion events have long been considered, in theory, as a possible and even likely outcome of the formation of early planetary systems, and may even have occurred earlier in our own Solar System.
A new perspective on the early formation of planetary systems
If this explanation proves to be correct, it will open a new window into the early history of planetary systems, allowing us to study the number and timing of planetary accretion.
Unlike isolated stars, those in clusters have well-defined ages and masses, and the presence of many similar “sister” stars born from the same source material means that even small differences in chemical composition are easier to detect, the researchers said.
According to phys.org
