![KOI-351 d: 8-Planet System, 0.320 AU Out](https://cdn.slatesource.com/5/4/7/5477a84a-86a3-4df5-b587-8adfb2874ed6.webp) # KOI-351 d: 8-Planet System, 0.320 AU Out - [Made in Slatesource](https://slatesource.com/@steph/koi-351-d-8-planet-system-0-320-au-out) - By [Steph](https://slatesource.com/@steph) - Created on Sep 19, 2026 ## Mini-neptune around KOI-351 It is 2.87 times Earth's radius, closest in size to Neptune. A year there lasts 59.74 days, on an orbit 1 times closer to its star than Mercury is to the Sun. Its equilibrium temperature is 519 K (derived from the star rather than measured), hotter than any desert. The host star KOI-351 runs at 6080 K with 1.20 times the Sun's mass. journey·5 Planets # KOI-351 from the inside out Orbit / Planet "super-Earth, 1080 K. "terrestrial, 985 K. "mini-Neptune, 519 K. "mini-Neptune, 453 K. "mini-Neptune, 424 K. Radius 2.87 Earth radii Equilibrium temperature 519 K (derived) One year 59.74 days Orbit radius 0.3200 AU Host star KOI-351 at 6080 K Distance 2767 light-years Starlight blocked 0.048% at each transit What a crossing measures The fraction of starlight blocked sets the radius against the star's. 🔭🪐📅01.01.2013 – 01.01.2017 01.01.2013KOI-351 b, KOI-351 c, KOI-351 d, KOI-351 e, KOI-351 f 01.01.2013 01.01.2017Kepler-90 i 01.01.2017 Known and unknown, as the archive has it 0% A radius from transit photometry. Yes. A measured mass. No. A density, which decides rock or gas. No. An orbital distance. Yes. A measured temperature rather than a derived one. No. The shape of the orbit. No. The archive lists no measured equilibrium temperature for this planet. The 519 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. Found by Kepler in 2013. Kepler's method needed repetition, not brightness. It could find small planets around faint stars, provided they came round quickly enough to be seen twice. The detection is a shadow crossing a disc. Shadows have no weight, which is the whole reason the mass column is empty. KOI-351 has 8 known planets. A crowded system is worth more than the sum of its planets: the timing of each transit constrains the others. # Half the temperatures quoted for exoplanets are calculated from the star, not \\ measured at the planet. Should a page like this show them at all, or leave the field blank? No comments yet. Be the first. Log in to comment [Every parameter ever published for KOI-351 d, at the NASA Exoplanet Archive](https://exoplanetarchive.ipac.caltech.edu/overview/KOI-351%20d?utm_source=slatesource)