Astronomers Find Evidence of Stars Engulfing Planets

A new study suggests six red dwarf stars have consumed rocky planets, temporarily boosting their lithium levels.

"This is exciting because evidence of planet-swallowing events has been long sought for. With my collaborators in Keele, we think that we have finally found the needles in the haystack."
– Professor Isabelle Baraffe, University of Exeter

Key Discovery

Researchers from the University of Exeter and Keele University have identified six red dwarf stars in three young star clusters that exhibit unexpectedly high levels of lithium in their atmospheres. The findings were made possible by analyzing data from the Gaia-ESO Spectroscopic Survey.

The team proposes that these stars have engulfed planets, which temporarily replenished their lithium. Using evolutionary models, the researchers estimate the stars may have consumed between three and ten Earth masses of rocky planetary material.

The Background

Red dwarf stars are among the most common stars in the galaxy. Their hot interiors should rapidly destroy lithium, making any significant amounts of the element highly unusual.

Planet-swallowing events have long been predicted during the chaotic early stages of planetary system formation. Scientists believe similar events may have occurred in the early Solar System as well.

What This Means

The study represents a major step forward in understanding the violent processes that shape planetary systems. By finding these "needles in the haystack," researchers have provided some of the strongest evidence yet that young stars can and do consume their own planets.