Why our solar system couldn’t have had a super Earth, a type of world that abounds throughout the galaxy, has long vexed astronomers. Now, a new study proposes an intriguing explanation: Maybe the sun ate it. Mutlu Yildiz, a professor of astronomy at Ege University in Turkey, used computer simulations to turn back the clock and study the young sun with and without a swallowed planet to see which version best fits the star we know today. Their models, which fed the Sun a dense, rocky super-Earth (five to ten times more massive than Earth and rich in heavy elements like Mercury), aligned closely with real measurements. Previous work has proposed that a super-Earth could have formed and then spiraled through space toward the Sun billions of years ago, but this paper is perhaps the first to delve deeper into the idea, asking whether the Sun retains evidence that such an event took place. “We believe it could,” Yildiz said in a statement. SEE ALSO: 3D map reveals galaxy cities taking shape in the early universe Lithium is one of the most important chemical clues pointing to the absorption of a planet. When the sun formed, it was made of the same material as meteorites and the gas cloud that surrounds it. From those rocks and gases, scientists can estimate how much lithium the newborn sun should have had. Today, the sun’s surface has more than 100 times less lithium than expected. Lithium atoms only break apart deep inside a star, where it is much hotter, so the missing element suggests that something could have dragged it down. Mashable Light Speed Artist’s rendering of a super-Earth orbiting a Sun-like star. Credit: Illustration by NASA/JPL-Caltech The new study, published in Monthly Notices of the Royal Astronomical Society, suggests a scenario in which the unfortunate planet brings back material poor in lithium but rich in heavier elements. Yildiz nicknamed the hypothetical planet Dev Dilek, which means “Great Wish” in Turkish. The name Dilek is traditionally associated with wishes directed to Mercury, and the prefix “Dev” means giant. Want more science and technology news delivered straight to your inbox? Sign up for Mashable’s Light Speed newsletter or receive push alerts from Mashable today. Mixing that lithium-poor material with the sun’s outer layers helps explain the lithium shortage. Meanwhile, extra-heavy elements buried just below the surface make models of the Sun’s interior (including how sound waves travel and how deep the churned outer layer goes) better align with what astronomers actually observe. The study also tests whether a rocky planet could realistically survive immersion in the Sun long enough to bring its material to the appropriate depth. Separate calculations track how a compact, iron-rich world behaves as it falls through hot solar gas. Under intense pressure, the planet shrinks, exposing a smaller area to the gas and reducing the rate at which its outer layers burn. In computer simulations, the planet loses only a fraction of its mass before reaching the base of the convection zone. That means most of its rocky core could end up exactly where solar models need it, according to the research. While Yildiz had a hunch that absorbing a planet could affect the structure of the sun, he didn’t expect the math to align so closely with a specific type of planet mass range. “That was one of the most interesting results,” he said. Astronomers already have evidence that stars can eat their planets. Some stars briefly glow and swell after engulfing nearby exoplanets, and subtle changes in the orbits of hot Jupiters suggest that many are slowly falling toward their stars. Studies of Sun-like stars also find chemical patterns that hint at past planetary meals. The new article places a mirror in front of our own star. While it doesn’t prove that the Sun devoured a super-Earth, it does show that a Sun with an early planetary feast matches better across a wide range of measurements than any model without it. “The next step is to see if these fingerprints can be detected independently,” Yildiz said.
