Astronomers have discovered some of the clearest evidence yet that stars can consume their own planets.
In a new study published in the journal Monthly Notices of the Royal Astronomical Society, researchers found signs that six young red dwarf stars had swallowed nearby rocky planets similar to Earth during the early stages of their planetary systems.
The research was carried out by scientists from Keele University and the University of Exeter, who examined thousands of stars in several young star clusters.
Their goal was to better understand what happens when planets and stars form together.
The clue came from an unexpected chemical element called lithium.
According to lead researcher Professor Robin Jeffries from Keele University, lithium should normally disappear from red dwarf stars shortly after they are born. Although red dwarfs are smaller and cooler than our Sun on the outside, their interiors are extremely hot. Those high temperatures quickly destroy lithium through nuclear reactions.
As a result, finding lithium in a red dwarf star is unusual.
“It’s a bit like throwing paint onto a blank canvas,” Professor Jeffries explained. Even a small amount of lithium stands out clearly because the stars should contain almost none of it.
Scientists have long suspected that if a red dwarf swallowed planet material rich in lithium, the element could briefly reappear in the star’s atmosphere. The new findings appear to support that idea.
Using data from the Gaia-ESO Spectroscopic Survey, which analyzes the light coming from stars, the researchers identified six red dwarfs with much higher lithium levels than similar stars in the same clusters.
The team believes the most likely explanation is that these stars consumed rocky planets orbiting nearby. Their calculations suggest each star may have swallowed the equivalent of about three to ten Earth masses of planetary material.
Planet engulfment has been predicted by astronomers for many years. During the chaotic early stages of planetary system formation, planets can migrate inward toward their host star and eventually be destroyed. Some scientists think similar events may even have occurred in the early history of our own solar system.
The discovery could provide a new way to study how planetary systems develop. Because stars in clusters are born at roughly the same time and from the same cloud of gas, researchers can more easily spot unusual chemical differences between them.
By identifying stars that have recently consumed planets, astronomers may gain valuable insights into how often these dramatic events occur and how young planetary systems evolve over time.
