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3d ago

UC Santa Cruz Model Recasts Sub‑Neptune ‘Steam Worlds’ With Colder, Smaller Interiors

The study uses laboratory measurements of water at extreme conditions to connect telescope spectra with interior evolution.

Image
An artist's concept of the exoplanet GJ 9827d, the smallest exoplanet where water vapor has been detected in the atmosphere. Image not associated with study in article.

Overview

  • The model, published July 24 in The Astrophysical Journal, was led by Artem Aguichine with co-authors Natalie Batalha and Jonathan Fortney at UC Santa Cruz.
  • It integrates experimental physics for supercritical water and superionic ice to produce more realistic interior and evolution predictions.
  • Results indicate smaller planetary radii and cooler deep interiors than earlier estimates, with water likely transitioning to superionic ice under extreme pressures and temperatures.
  • JWST has confirmed steam in the atmospheres of several sub-Neptunes, supplying observations that can test these predictions.
  • Upcoming measurements, including from ESA’s PLATO mission, are expected to evaluate and refine the framework and help prioritize targets in searches for water-rich worlds.