ESA/Hubble
Artist’s rendering of two Earth-sized worlds passing in front of their red dwarf star in the TRAPPIST-1 system, 40 light years away
Astronomers have discovered some of the strongest evidence to date that stars can swallow their own planets.
A new one, published in the magazine Monthly Notices of the Astronomical Societycorroborates the long-held belief that young stars are capable of “eat” nearby worlds as planetary systems form.
Researchers at Keele University and the University of Exeter studied thousands of stars and found evidence that six red dwarfs different stars (the smallest, coldest and most common type of star in the Universe) had swallowed rocky planets Earth-like.
What revealed this was the chemical “fingerprint” highly detectable, said lead author Professor Robin Jeffriesfrom Keele University. “We discovered that some of the red dwarfs we studied contained lithiuma chemical element that shouldn’t be there”, he explained.
“So even a small amount of lithium stands out clearly in these stars – a bit like throwing paint onto a blank canvas“.
Professor Jeffries adds that red dwarfs are smaller and colder than our Sun, but inside onlyare extremely hot. “This heat should destroy all of its fragile lithium in nuclear reactions shortly after its formation”, he highlights.
For this reason, there were already previous predictions that the detection of lithium in their atmospheres could indicate the absorption of material still rich in lithiumoriginating from a surrounding planetary system.
In the new study, researchers analyzed clusters of young stars using spectroscopic data, which refers to the study of how different types of matter interact with electromagnetic radiation.
Data from the GES (Gaia-ESO Spectroscopic) survey covered thousands of stars, of which the team identified six different red dwarfs in three distinct clusters that presented a much higher lithium content to that of other stars of similar spectral type.
The analysis suggests that these stars will have “swallowed” in a dramatic way the Earth-like planets that surrounded them, that is, about 3 to 10 Earth masses of planetary material in total, providing a fresh injection of lithium to their otherwise lithium-depleted atmospheres.
It has long been theorized that these absorption events constitute a possible and even probable outcome during the initial phase of training of planetary systems, and may even have occurred at an earlier stage in our own Solar System.
If this explanation turns out to be correct, a new window will have opened to the beginnings of planetary systems, allowing us to investigate the amount and timing at which planetary absorption occurred.
Unlike isolated stars, those found in clusters have well-known ages and masses, and the presence of many similar sisters born from the same starting material means that even small differences in chemical abundance are easier to determine, researchers said.
