New Delhi: An analysis of spectroscopic data from the Gaia survey of the European Southern Observatory has revealed anomalous chemical signatures of six
M-dwarf or red dwarf stars. The six red dwarf stars are located across three separate young star clusters, NGC 2451a, Blanco 1 and NGC 2516. The stars are between 50 million and 200 million years in age, for comparison the Sun is about 4.6 billion years old. The stars are structurally and kinematically indistinguishable from their stellar cousins, except for a massive enrichment of lithium in their outer atmospheres. A lithium-rich atmosphere indicates that the star has recently fed on a planet.
The interiors of red dwarf stars are extremely hot and turbulent that typically destroy primordial lithium within nuclear reactions during the early stages of their lives. Consequently, stars of this age and spectral class should show virtually no trace of lithium. The six identified outliers exhibit a distinct lithium signature and a narrow temperature range. Advanced evolutionary models indicate that this replenishment of atmospheric lithium was triggered by the ingestion of planetary material. The calculations indicate that these stars consumed the equivalent of three to ten Earth masses, of rocky planetary matter, depleted of volatiles.
Lithium signature can reveal gluttonous stars
The accretion events, where the stars swallowed the planets must have occurred after the stars developed a stable, radiative core, preventing the freshly added lithium from being pulled deep into the interior and destroyed. This also provides planets with sufficient time to form from the material leftover from the creation of their host stars, before being destroyed after short lives. Dynamical interactions and gravitational instability during the chaotic infancy of a star system frequently force young planets to spiral into their host stars. The discovery needs to be verified by further research, but tracking this specific chemical fingerprint offers a powerful new technique to map the frequency of planetary destruction, and the structural evolution of exoplanetary systems across the galaxy.
