TOI-6716 b is a confirmed terrestrial exoplanet orbiting a cool M-type dwarf star approximately 18.9 parsecs from Earth. It was identified through transit observations, a method in which astronomers detect periodic dips in a star’s brightness caused by a planet passing in front of it. The planet was formally announced as a confirmed discovery in 2026 following multi-instrument validation efforts that combined space-based photometry and ground-based follow-up observations to rule out false positives and refine its physical parameters.
The planet is remarkably similar in size to Earth, with a radius of about 0.98 Earth radii, placing it firmly in the category of rocky, Earth-sized worlds rather than gas or ice giants. Its mass is estimated at roughly 0.91 Earth masses, indicating that it likely has a comparable bulk density to Earth, suggesting a primarily rocky composition with a possible iron-rich core. These properties make it one of the more precisely characterized Earth-sized exoplanets discovered in recent TESS-era surveys of nearby red dwarf systems.
TOI-6716 b orbits extremely close to its host star, completing one full orbit in approximately 4.7 days at a distance of only about 0.032 astronomical units. This places it far inside Mercury’s orbital distance in our own Solar System and exposes it to a much stronger stellar radiation environment than Earth experiences. Despite this proximity, its stellar host is a cool red dwarf with an effective temperature of roughly 3100–3200 K, meaning the planet receives a different spectral energy distribution dominated by infrared radiation rather than visible light.
Because of its short orbital period and close-in orbit, TOI-6716 b is likely tidally influenced by its star, meaning it may rotate synchronously or near-synchronously, with one hemisphere perpetually facing the star. This configuration is common among close-in planets around low-mass stars and has important implications for atmospheric dynamics, heat redistribution, and long-term climate stability if the planet retains a substantial atmosphere.
Despite its proximity to its star, TOI-6716 b is of particular scientific interest because of its position near the inner edge of the so-called temperate or habitable-zone flux range for low-mass stars. Estimates suggest it receives a stellar energy flux of roughly 4–5 times that of Earth, placing it near the boundary where rocky planets may transition from temperate conditions to runaway greenhouse states, depending on atmospheric composition and albedo. This makes it an important case study for understanding the limits of habitability around M-dwarf stars.
Its host star, TOI-6716, is a small, cool red dwarf with a radius of about 0.23 times that of the Sun and a surface temperature close to 3200 K. Such stars are long-lived and stable compared to Sun-like stars, but they can also exhibit magnetic activity, including flares and enhanced ultraviolet emission, especially in their early evolutionary stages. This activity can influence atmospheric retention on closely orbiting planets, potentially stripping lighter gases over time or altering atmospheric chemistry.
From a formation perspective, TOI-6716 b likely originated further out in its protoplanetary disk before migrating inward, as in-situ formation at such close orbital distances is difficult under standard planet formation models. Planetary migration driven by disk interactions is a leading explanation for many short-period terrestrial and super-Earth-sized planets discovered by transit surveys such as NASA’s Transiting Exoplanet Survey Satellite mission.
The combination of its Earth-like size, short orbital period, and proximity makes TOI-6716 b a valuable target for future atmospheric characterization attempts. If it retains even a thin atmosphere, transmission spectroscopy during transits could potentially reveal the presence of molecules such as water vapor, carbon dioxide, or other volatiles, offering insight into whether rocky planets around M-dwarfs can maintain atmospheres under strong stellar irradiation.
Overall, TOI-6716 b represents a key example of the growing population of well-characterized terrestrial exoplanets orbiting nearby red dwarfs. These worlds are central to modern exoplanet science because they allow researchers to test models of planetary structure, atmospheric evolution, and habitability under conditions very different from those found in the Solar System, while still remaining observationally accessible with current and next-generation telescopes.
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