The sun may once have swallowed a super-Earth planet and could still be hiding the evidence
Our star and primary energy source that makes life on this planet possible may also be a cosmic cannibal. That’s according to new research that suggests the sun may have swallowed a super-Earth planet billions of years ago in its early history. And our star may still be hiding the evidence.
The scientists behind this research think that the fingerprints of this violent consumption of a planet may still exist within the solar interior. Super-Earths are common occupants of other planetary systems, and these findings can explain why the solar system lacks such a world.
“Our new study suggests that a planet several times more massive than Earth may have fallen into the young sun and left a lasting chemical imprint deep inside it,” Mutlu Yildiz, of Ege University, Turkey, said in a statement.
Yildiz and colleagues theorize that the sun’s act of planetary infanticide may help to explain differences between observations of the sun and what is predicted by models of stellar evolution. This includes the depth of the sun’s convection zone and the so-called sound-speed structure just below the convection zone.
It could also explain why the surface of the sun is depleted of the element lithium.
“By modelling the sun’s evolution and comparing the results with precise observations of its interior, we find that the ingestion of a super-Earth could help explain long-standing differences between standard solar models and observations, including subtle changes in the sun’s internal structure and its depleted lithium abundance,” Yildiz said. “We were interested in whether these problems might have a common origin in the early chemical history of the sun.”
The researcher explained that young stars like the sun during its infancy are surrounded by vast flattened clouds of gas and dust called protoplanetary discs, where substantial amounts of material can move between the disc and the star.
“Since planets are made of material that is chemically different from the gas in the disc, we wondered whether the early engulfment of a planet could have left a chemical signature inside the young sun,” Yildiz said.
What happened to the sun’s planetary meal?
Using advanced stellar evolution software, Yildiz and colleagues tested their idea by investigating different ways the sun could have swallowed a planet.
Their results found the best fit for the sun’s current characteristics was the cannibalism of a planet between five and ten times the mass of the Earth, a type of planet called a super-Earth. This could explain the strange, unpredicted characteristics of the sun.
We thought planetary engulfment might affect the solar structure but did not expect the calculations to converge on such a specific super-Earth mass range,” said Professor Yildiz. “That was one of the most interesting outcomes of the study.”
The team’s research is supported by previous studies that suggests one or more super-Earth planets could have formed with the orbit of Mercury, the closest planet to the sun.
These worlds would have then migrated through the protoplanetary disk surrounding the infant sun before crashing into the star.
But this new study leaves open the possibility that something else, other than this violent collision with the sun, may explain the discrepancies in measurements of the sun’s interior and its lithium content. The team’s model doesn’t need a planet to have been totally engulfed by the sun.
Currently, this idea is based on computer modelling and unexplained solar features, but the researchers think that the predicted structural and chemical signature of a planetary engulfment could still exist within our star and could be detected.
“The earlier work proposed that a super-Earth could have formed and migrated into the young sun. Our paper asks whether the sun itself could still carry observable evidence that such an engulfment actually happened, and we believe it could,” Yildiz concluded. “The next step is to see if these fingerprints can be independently detected.”
The research was published on Thurs (Sept. 10) in the journal Monthly Notices of the Royal Astronomical Society.