Did Sun eat super-Earth? New study says maybe

The sun's surface holds over 100 times less lithium than it should, based on the raw materials it formed from, and a Turkish astronomer thinks he knows where that lithium went: into digesting a planet.

The computer simulations that compared the scenario of a young sun devouring a planet with the scenario when the young sun did not were performed by Mutlu Yildiz, the astronomy professor of Ege University.

The simulations showed that the first scenario correlated much better with what we can observe with the help of telescopes today. It was published in Monthly Notices of the Royal Astronomical Society this year.

Lithium disintegration is possible only under the extremely high temperatures existing inside a star, but not near its surface.

Therefore, a young star could conserve most of its lithium. Such a shortage of lithium in a star means that there must be some force attracting to a star the material poor in lithium but rich in metals, different from the material that makes up the star.

Yildiz named the hypothetical planet Dev Dilek, Turkish for "Great Wish", a nod to Mercury's traditional association with wishes and the word for "giant".

A planet falling into the sun wouldn't necessarily vaporise instantly. Yildiz's calculations show that under the crushing pressure of the sun's outer gas layers, a compact, iron-rich world shrinks in on itself, shedding less mass than expected as it falls.

In his models, the planet retains most of its core all the way down to the base of the sun's convection zone, precisely the depth the solar models need it to reach.

The surviving central material can also help solve other theoretical-observational discrepancies, such as the propagation of sound waves through the sun and the depth of the convective layer of the sun.

Other stars have been observed brightening and expanding due to feeding on exoplanets within their close proximity, and hot Jupiters are known to be slowly drifting towards the stars they are orbiting. There have been chemical signatures of similar events in sun-like stars as well.

Yildiz's work doesn't prove the sun ate a super-Earth, only that the theory fits the data better than any alternative tested so far.