Twice-Earth-Sized Hot Sub-Neptune TOI-5734 b Uncovered

An international team using TESS and HARPS-N confirmed TOI-5734 b, a hot sub-Neptune about 2.1 Earth radii and 9.1 Earth masses orbiting the young K-dwarf TOI-5734 every 6.18 days at roughly 0.06 AU (about 106 light-years away). With an equilibrium temperature around 688 K, the planet lies near the upper edge of the radius valley and is likely rocky with a largely stripped atmosphere, though a water-world scenario cannot be ruled out. The discovery, described in a February 2026 arXiv paper (DOI 10.48550/arxiv.2602.18108), leveraged three TESS sectors and HARPS-N data to illuminate atmospheric loss and inward migration in close-in exoplanets.