The Stripped Planetary Core of the Super-Earth TOI-849 b
Deep within the constellation of Puppis, approximately 730 light-years from our solar system, resides one of the most enigmatic objects discovered by modern transit surveys: TOI-849 b. This object occupies a unique place in the census of exoplanets, acting as a bridge between the realms of terrestrial worlds and gas giants. It is a world of extreme density, a remnant of a larger structure that has shed its gaseous shroud, leaving behind only the most fundamental components of its formation.
TOI-849 b is classified as a hot super-Earth, but it possesses the mass of a gas giant—roughly twice that of Neptune. Its density is remarkably high, suggesting that it is composed primarily of a rocky, metallic core with little to no remaining hydrogen or helium envelope. Astronomers hypothesize that this world was once a much larger, gas-shrouded planet, but through a process of intense photoevaporation or dynamical stripping, its outer layers were systematically removed, exposing the heart of the world to the harsh radiation of its host star.
The physical profile of TOI-849 b is defined by its extreme proximity to its host star, a G-type star slightly more massive than our Sun. This proximity forces the mass of the object to endure a constant, withering thermal environment. With orbital periods lasting less than 24 hours, the surface of this object is subjected to temperatures exceeding 1,500 degrees Celsius. This heat is not just an ambient condition; it is a primary driver of the ongoing geologic and physical evolution of the crust.
Geologically, TOI-849 b represents an anomaly in the planetary formation model known as the Neptune Desert. In this region of close-in orbital space, gas giants are typically rare because their gaseous envelopes are rapidly stripped away by stellar winds and high-energy radiation. TOI-849 b serves as a definitive case study for this phenomenon, having survived the loss of its outer layers while maintaining a core mass that defies standard evolutionary trajectories. Its interior is likely composed of a high-pressure silicate mantle surrounding a massive core of iron and nickel, crushed to an extreme state by the self-gravity of such a significant body.
The surface, if a landing were possible, would be a desolate landscape of basaltic plains and pools of molten minerals. Given the tidal forces at play, the topography is likely dominated by thermal expansion and contraction, creating a rugged, cracked surface that reflects the violent history of the object’s formation. There are no oceans, no ice, and no volatile gases—only a dry, incandescent husk of rock and metal.
As we continue to observe this object, it challenges our understanding of core-envelope dynamics. By stripping away the outer layers, the host star has performed a natural autopsy, laying bare the materials that normally reside deep beneath layers of hydrogen and helium. TOI-849 b remains a testament to the violent forces that govern the evolution of planetary bodies in the proximity of their parent stars.
