![Top-down, to-scale view of the TOI-789 architecture. The four planetary orbits are drawn around the M3 host (center); symbol size scales with planetary radius and symbol color with equilibrium temperature (color bar). The candidate .04 is drawn with a dashed outline. Shaded annular bands mark, from the inside out, the Venus zone (Kane et al. 2014), the temperate region defined by Teq = 273– 400 K, and the inner edge of the Kopparapu et al. (2014) habitable zone. The four planets form a sequence of decreasing insolation that crosses the Venus zone, with the candidate .04 near the inner edge of the habitable zone.-- [astro-ph.EP]](https://i0.wp.com/astrobiology.com/wp-content/uploads/2026/09/Characterization.png?fit=1200%2C674&ssl=1)
[astro-ph.EP] We present the validation and dynamical characterization of TOI-789 (TIC 300710077), a compact multi-planet system around an M3 dwarf at 43 pc.
Using ~7 yr of TESS photometry (42 sectors), public ground-based follow-up (LCOGT, MEarth), and high-resolution imaging (Gemini/Zorro, SOAR), we statistically validate three terrestrial planets with TRICERATOPS: TOI-789 b (Rp = 1.18 Rearth, P = 5.45 d), c (1.15 Rearth, 8.04 d), and d (1.40 Rearth, 12.97 d), with false-positive and nearby-false-positive probabilities below the validation thresholds once resolved neighbours are excluded using the on-target ground-based photometry.
Through an iterative Transit Least Squares search we identify a fourth, previously uncatalogued planet candidate (P = 19.74 d, Rp ~ 0.88 Rearth), the outermost and most temperate member (S = 1.71 Searth, Teq ~ 292 K); its low signal-to-noise ratio precludes formal validation, so we report it as a candidate pending confirmation.
A dynamical analysis (SPOCK and N-body integrations) indicates a dynamically cold, near-resonant system, stable only for low eccentricities (e < 0.05), eccentricity rather than mass limiting stability; including the fourth candidate tightens this further.
The four objects span the Earth-Venus transition across the Venus zone, two validated planets falling in the temperate regime under the equilibrium-temperature criterion, making the system a potential comparative-planetology laboratory anchored on confirmed planets.
The low TSM (~3-5) and moderate host brightness place atmospheric characterization beyond reach. TOI-789 exemplifies the numerically dominant population of compact terrestrial-planet systems around M dwarfs whose characterization is limited by host brightness, for which dynamical characterization offers a complementary route.
Juan F. Pagés Navarrete
Comments: Accepted for publication in The Astronomical Journal. 21 pages, 12 figures, 5 tables
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2609.22945 [astro-ph.EP] (or arXiv:2609.22945v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2609.22945
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Related DOI:
https://doi.org/10.3847/1538-3881/aea6c9
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Submission history
From: Juan Francisco Pagés Navarrete
[v1] Sat, 19 Sep 2026 10:52:57 UTC (3,801 KB)
https://arxiv.org/abs/2609.22945
Astrobiology,
