Two Temperate Earth- and Neptune-sized Planets Orbiting Fully Convective M dwarfs

As the diversity of exoplanets continues to grow, it is important to revisit assumptions about habitability and classical HZ definitions. In this work, we introduce an expanded ‘temperate’ zone, defined by instellation fluxes between 0.1<S/S_⊕<5, thus encompassing a broader range of potentially habitable worlds.

We also introduce the TEMPOS survey, which aims to produce a catalogue of precise radii for temperate planets orbiting M dwarfs with T_eff≤3400 K. This work reports the discovery and characterisation of two planets in this temperate regime orbiting mid-type M dwarfs: TOI-6716 b, a 0.98±0.07R_⊕ planet orbiting its M4 host star (R⋆=0.231±0.015R_⊙, M⋆=0.223±0.011M_⊙, T_eff=3110±80K) with a period P=4.7185898+0.0000054−0.0000041d, and TOI-7384 b, a 3.56±0.21R_⊕ planet orbiting an M4 (R⋆=0.319±0.018R_⊙, M⋆=0.318±0.016M_⊙, T_eff=3185±75K) star every P=6.2340258+0.0000034−0.0000036d.

The radii of TOI-6716 b and TOI-7384 b have precisions of 6.8% and 5.9% respectively. We validate these planets with multi-band ground-based photometric observations, high-resolution imaging and statistical analyses. We find these planets to have instellation fluxes close to the inner (hotter) edge of the temperate zone, with 4.4±1.1S_⊕ and 4.9±1.1S_⊕ for TOI-6716 b and TOI-7384 b respectively.

Also, with a predicted TSM similar to the TRAPPIST-1 planets, TOI-6716 b is likely to be a good rocky-world JWST target, should it have retained its atmosphere.

Stellar mass vs instellation flux for transiting planets with 0.4 < 𝑅_𝑝 < 4 R_⊕ and 𝑀_𝑝 < 500 M_⊕ obtained from the Composite NASA exoplanet archive (grey points). Instellation flux recalculated for all planets for consistency. Approximate spectral types are indicated by the shaded background and highlighted labels. Planets for which SPECULOOS observations contributed to the validation/confirmation are highlighted with blue circles. TOI-6716 b and TOI-7384 b are depicted by red diamonds, and sit at the inner (hotter) edge of the temperate regime (shown by the green box). — astro-ph.EP

Madison G. Scott, Georgina Dransfield, Mathilde Timmermans, Amaury H.M.J. Triaud, Benjamin V. Rackham, Khalid Barkaoui, Adam J. Burgasser, Karen A. Collins, Michaël Gillon, Steve B. Howell, Alan M. Levine, Francisco J. Pozuelos, Keivan G. Stassun, Carl Ziegler, Yilen Gomez Maqueo Chew, Catherine A. Clark, Yasmin Davis, Fatemeh Davoudi, Tansu Daylan, Brice-Olivier Demory, Dax Feliz, Akihiko Fukui, Maximilian N. Günther, Emmanuël Jehin, Florian Lienhard, Andrew W. Mann, Clàudia Janó Muñoz, Norio Narita, Peter P. Pedersen, Richard P. Schwarz, Avi Shporer, Abderahmane Soubkiou, Sebastián Zúñiga-Fernández

Comments: 22 pages, 15 figures, accepted for publication in MNRAS
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2601.05799 [astro-ph.EP] (or arXiv:2601.05799v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2601.05799
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Submission history
From: Madison Scott
[v1] Fri, 9 Jan 2026 13:57:46 UTC (8,097 KB)
https://arxiv.org/abs/2601.05799

Astrobiology, exoplanet,