New model finds the lower size limit for habitable exoplanets

The search for Earth 2.0 has begun in earnest. But there's a huge variety of exoplanets out there, so narrowing down the search to focus valuable telescope time on only the best candidates is critical. One variable of a planet that will have a huge impact on its habitability is its size. A new paper, now available in preprint on arXiv, by researchers at the University of California Riverside, looks into the impact of a planet's size on one of its more critical features for habitability—whether it holds onto an atmosphere—and determines that slightly smaller than Earth is likely the smallest...