What question did this study set out to answer?

This research aims to confirm the existence of TOI-2431 b, a planet with an extremely short orbital period around a K dwarf star.

February 2, 2026

An Earth-sized planet on a 5.4h orbit around a nearby K dwarf

Puntos clave

This research aims to confirm the existence of TOI-2431 b, a planet with an extremely short orbital period around a K dwarf star.
Used observations from the Transiting Exoplanet Survey Satellite (TESS)
Employed precise radial velocities with NEID and Habitable-zone Planet Finder (HPF)
Conducted ground-based high-contrast imaging with NESSI
TOI-2431 b has an orbital period of 5 hours and 22 minutes, indicating it's one of the shortest-period exoplanets known.
It has a radius of 1.534 ± 0.033 Earth radii and a mass of 6.2 ± 1.6 Earth masses.
The planet's density suggests an Earth-like composition and that it is likely a 'lava-world'.
Estimated orbital decay timescale is only ∼31 million years, indicating a near-Roche-limit orbit.
The star's brightness gives TOI-2431 b a high emission spectroscopy metric of 27, favorable for atmospheric studies.

Resumen

We present the discovery and confirmation of the ultrashort period (USP) planet TOI-2431 b orbiting a nearby (d = 4109 ± 28, pc) late K star (T_ eff ̊m K) using observations from the Transiting Exoplanet Survey Satellite (TESS), precise radial velocities (RVs) with NEID and Habitable-zone Planet Finder (HPF) spectrographs, as well as ground-based high-contrast imaging from NESSI. TOI-2431 b has a period of 5 hours and 22 minutes, making it one of the shortest-period exoplanets known to date. TOI-2431 b has a radius of 1. 534 ± 0. 033, R_⊕ and a mass of 6. 2 ± 1. 6, M_⊕, where the exact mass precision shows a slight dependence on the choice of prior. This suggests TOI-2431 b has a density compatible with an Earth-like composition and due to its high irradiation, it is likely to be a "lava-world" with a T_ eq = 2063 ± 30, ̊m K. We estimate that the current orbital period is only 30% larger than the Roche-limit orbital period and that it has an expected orbital decay timescale of only ∼31 Myr. Finally, due to the brightness of the host star (V = 10. 9, K = 7. 6), we find that TOI-2431 b has a high emission spectroscopy metric (ESM) of 27, making it one of the best USP systems for atmospheric phase-curve analyses.

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