Hundreds of TESS exoplanets might be larger than we thought

TL;DR

This study reveals that many TESS exoplanet radii are underestimated due to blending with background stars, affecting our understanding of their composition and the overall exoplanet population.

Contribution

The paper introduces a validated deblending methodology that corrects systematic biases in TESS exoplanet radius measurements, highlighting widespread underestimations in previous studies.

Findings

Median radius underestimation of 6.1% in literature

Results in about 20% overestimation of planet density

Impacts interpretations of exoplanet composition and formation theories

Abstract

The radius of a planet is a fundamental parameter that probes its composition and habitability. Precise radius measurements are typically derived from the fraction of starlight blocked when a planet transits its host star. The wide-field Transiting Exoplanet Survey Satellite (TESS) has discovered hundreds of new exoplanets, but its low angular resolution means that the light from a star hosting a transiting exoplanet can be blended with the light from background stars. If not fully corrected, this extra light can dilute the transit signal and result in a smaller measured planet radius. In a study of hundreds of TESS planet discoveries using deblended light curves from our validated methodology, we show that systematically incorrect planet radii are common in the literature: studies using various public TESS photometry pipelines have underestimated the planet radius by a weighted median of $6.1\% \pm 0.3\%$, leading to a $\sim20\%$ overestimation of planet density. The widespread presence of these biases in the literature has profoundly shaped-and potentially misrepresented-our understanding of the exoplanet population. Addressing these biases will refine the exoplanet mass-radius relation, reshape our understanding of exoplanet atmospheric and bulk composition, and potentially inform prevailing planet formation theories.