A new preprint on arXiv introduces a clear physical framework for classifying the main heat sources driving exoplanet surface temperatures by comparing stellar irradiation to tidal heating. The authors developed a dimensionless ratio called Lambda (F_abs / F_tide) to determine which energy mechanism dominates.

The study applied this method to a sample of approximately 2000 exoplanets. Results show that most planets' thermal environments are governed by absorbed starlight, though a significant fraction have tidal heating as the primary driver. The researchers define a boundary at Lambda = 1 where both fluxes are comparable, with orbital distance (semi-major axis) and orbital eccentricity emerging as the strongest influences on tidal heating.

This is a preprint (arXiv:2603.23557v1) and has not undergone peer review. Limitations include reliance on current exoplanet catalogs that contain uncertainties in orbital parameters for many systems, as well as model assumptions used to calculate tidal flux. The source is available at https://arxiv.org/abs/2603.23557.