![TOI-700 d: Habitable Zone, 37-Day Year](https://cdn.slatesource.com/d/9/9/d99f3a70-e47f-4ef1-9be0-aaf35944115c.webp) # TOI-700 d: Habitable Zone, 37-Day Year - [Made in Slatesource](https://slatesource.com/@steph/toi-700-d-habitable-zone-37-day-year) - By [Steph](https://slatesource.com/@steph) - Created on Sep 19, 2026 ## Terrestrial around TOI-700 It is 1.07 times Earth's radius, closest in size to Earth. A year there lasts 37.42 days, on an orbit 2 times closer to its star than Mercury is to the Sun. Its equilibrium temperature is 245 K (derived from the star rather than measured), in the range where liquid water is possible. The host star TOI-700 runs at 3459 K with 0.41 times the Sun's mass. What this planet has and has not got 0% Inside the habitable zone, computed from the star's luminosity. Yes. A measured mass, not just a radius. No. A measured temperature rather than one derived from the star. No. Any detection of an atmosphere. Not recorded in the archive. journey·4 Planets # TOI-700 from the inside out Orbit / Planet "terrestrial, 380 K. "mini-Neptune, 325 K. "terrestrial, 270 K. "terrestrial, 245 K. Radius 1.07 Earth radii Equilibrium temperature 245 K (derived) One year 37.42 days Orbit radius 0.1633 AU Host star TOI-700 at 3459 K Distance 102 light-years Starlight blocked 0.054% at each transit What you get from the shadow The fraction of starlight blocked sets the radius against the star's. 🔭🪐📅01.01.2020 – 01.01.2023 01.01.2020TOI-700 b, TOI-700 c, TOI-700 d 01.01.2020 01.01.2023TOI-700 e 01.01.2023 The archive lists no measured equilibrium temperature for this planet. The 245 K quoted here is derived from the star's output and the orbital distance, assuming a third of the light is reflected. It is an estimate from two numbers, not an observation. A transit is a silhouette. It gives a width and says nothing about how heavy the thing casting it is, so this planet has no mass on record. TOI-700 has 4 known planets. Systems like this are the ones where architecture can be studied instead of guessed at. Found by Transiting Exoplanet Survey Satellite (TESS) in 2020. TESS scans most of the sky in 27-day stretches, so it favours bright nearby stars and short orbits over the faint distant ones Kepler specialised in. # TOI-700 d sits in the habitable zone on the arithmetic alone. That says where \\ it orbits, not what it is like. What would you want measured next before calling it promising? No comments yet. Be the first. Log in to comment [NASA Exoplanet Archive: source data, including the values not used here](https://exoplanetarchive.ipac.caltech.edu/overview/TOI-700%20d?utm_source=slatesource)