A new paper recently published in Publications of the Astronomical Society of the Pacific explores whether tightly packed planetary systems can host habitable worlds over billions of years. The paper, Dynamical Interactions and Habitability in the TOI-700 Multi-planet System, was led by Coleman Nelson, a 2025 undergraduate alumni of the University of Wisconsin–Madison.
The study focuses on the TOI-700 system, which contains two Earth-sized planets—TOI-700d and TOI-700e—that receive potentially habitable levels of input radiation from their host star. Using the planetary evolution code VPLanet, Coleman modeled orbital dynamics, tidal locking, stellar evolution, and atmospheric water loss to test whether planet–planet interactions threaten long-term habitability. His work showed that gravitational interactions in this compact system do not destabilize the habitability prospects of either planet. However, while TOI-700d appears to be a robust habitable-zone planet, TOI-700e sits right on the edge of habitability, residing at the boundary of the tidally-locked habitable zone. This means that its habitability is sensitive to details like atmosphere composition and initial water inventory. Together, these results position TOI-700 as a prime target for future habitability studies, whether you’re looking for a solid habitable candidate (TOI-700 d) or a risky one that might not actually be habitable (TOI-700 e).
Congratulations to Coleman on the official publication of his excellent work!