Two Earth-size Planets and an Earth-size Candidate Transiting the nearby Star HD 101581^*

We report the validation of multiple planets transiting the nearby (\(d = 12.8\) pc) K5V dwarf HD 101581 (GJ 435, TOI-6276, TIC 397362481). This system consists of at least two Earth-size planets whose orbits are near a mutual 4:3 mean-motion resonance, HD 101581 b (\(P = 4.47\) days) and HD 101581c (\(P = 6.21\) days). Both planets were discovered in Sectors 63 and 64 TESS observations and statistically validated with supporting ground-based follow-up. We also identify a signal that probably originates from a third transiting planet, TOI-6276.03 (\(P = 7.87\) days). These planets are remarkably uniform in size and their orbits are evenly spaced, representing a prime example of the “peas-in-a-pod” architecture seen in other compact multiplanet systems. At \(V = 7.77\), HD 101581 is the brightest star known to host multiple transiting planets smaller than \(1.5\,R_\oplus\). HD 101581 is a promising system for atmospheric characterization and comparative planetology of small planets.

Recommended citation: Kunimoto, Michelle and Lin, Zifan and Millholland, Sarah et al. (2024). "Two Earth-size Planets and an Earth-size Candidate Transiting the nearby Star HD 101581^*." The Astronomical Journal.
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