Exoplanets, -moons, -comets

Hundreds Of TESS Exoplanets Might Be Larger Than We Thought

By Keith Cowing
Status Report
astro-ph.EP
June 26, 2025
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Hundreds Of TESS Exoplanets Might Be Larger Than We Thought
Planet mass-radius and mass-density distributions of literature and TGLC-fitted values. a, Mass-radius distribution of small TESS planets. b, Mass-density distribution of small TESS planets. Both panels include the high-precision planet sample with TESS-free literature values (gray diamond) and TESS-dependent TGLC-fitted values (black empty circle). The error bars represent 1σ Gaussian standard deviations. For each TESS-dependent TGLC-fitted value, a line connects it to the corresponding literature value, where the color of the line shows whether it increased (green) or decreased (orange) from the literature value. We also include theoretical models of planet compositions for the Earth-like (red), water worlds (blue), and rocky planets with atmospheres (brown). The last model accounts for the boil-off initial conditions (solid brown) and a range of agnostic initial conditions (region between dashed brown). Earth and Neptune are included for reference. — astro-ph.EP

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%±0.3%, leading to a ∼20% 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.

Te Han, Paul Robertson, Timothy D. Brandt, Shubham Kanodia, Caleb Cañas, Avi Shporer, George Ricker, Corey Beard

Comments: 20 pages, 3 figures, 4 tables, accepted by ApJL
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM)
Cite as: arXiv:2506.19985 [astro-ph.EP] (or arXiv:2506.19985v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2506.19985
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Submission history
From: Te Han
[v1] Tue, 24 Jun 2025 20:00:03 UTC (511 KB)
https://arxiv.org/abs/2506.19985
Astrobiology,

Keith Cowing

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻

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