Researchers believe that Kronos, a Sun-like star, has consumed up to a dozen rocky planets over the course of its life. In this artist’s concept, a parent star is devouring a planet.
Adrian Price-Whelan, a co-author of the study, explained that eating gas giants would not give the same results, even if they had rocky cores. “If you were to take Jupiter and throw it into a star,” he said, “Jupiter also has this huge gaseous envelope, so you’d also enhance carbon, nitrogen — the volatiles that Semyeong mentioned.” Instead, you would need to feed Kronos a bunch of smaller planets to account for its composition.
Though the exact process that led to Kronos devouring its inner planets is not known, Oh and her colleagues have some theories. The leading one is that Kronos and Krios once flew to close to another star, which stretched out the orbits of Kronos’s outermost planets. This caused the outer planets to careen through the inner solar system, in turn catapulting the rocky inner planets into death-spiral orbits with Kronos. Their theory, however, would require that Krios managed to somehow avoid a similar doomsday scenario. But considering the twin stars are so far apart that they only orbit each other about once every 10,000 years, it is entirely possible.
Equipped with their results, Oh and Price-Whelan both believe future study of the Kronos-Krios system is needed to help understand how different solar systems can form and evolve over time. “One of the common assumptions (well-motivated, but it is an assumption) that’s pervasive through galactic astronomy right now is that stars are born with [chemical] abundances, and they then keep those abundances,” Prince-Whelan said. “[Kronos] is an indication that, at least in some cases, that is catastrophically false.”