Could the TRAPPIST-1 planets be hiding a shocking secret about their cores? The TRAPPIST-1 system, with its seven Earth-sized planets orbiting an ultracool dwarf star, has captivated astronomers as a potential treasure trove for understanding exoplanet formation. But here's where it gets controversial: these planets are less dense than our own rocky neighbors, sparking a debate about their internal structure. Could they be coreless, lacking the iron-rich cores we see in Earth and other terrestrial planets?
And this is the part most people miss: a new study by Dongyang Huang and Caroline Dorn challenges this idea. Using advanced models of how metals and silicates separate during planetary formation, they show that oxygen behaves differently in these planets, becoming more attracted to iron. This means that even if these planets started with Earth-like compositions, they wouldn't have enough oxygen to completely oxidize their cores, ruling out the coreless scenario for planets up to four times Earth's mass.
Instead, the researchers suggest that the lower densities might be due to a different factor: the specific mix of elements available during the planets' formation, influenced by the star's own metallicity. This finding highlights the intricate dance between a star and its planets, shaping their very essence.
This study, published on arXiv [https://doi.org/10.48550/arXiv.2511.01231], raises intriguing questions: Are coreless planets truly rare, or are we simply looking in the wrong places? How does stellar metallicity ultimately shape the destiny of planets? The TRAPPIST-1 system, with its unique characteristics, continues to be a fascinating laboratory for unraveling these cosmic mysteries.
What do you think? Could there be coreless planets out there, or is the TRAPPIST-1 system a special case? Share your thoughts in the comments below!
