![KOI-351 c: 8-Planet System, 0.089 AU Out](https://cdn.slatesource.com/8/f/e/8fed198b-dee0-48d0-9554-0ce2ea426afe.webp) # KOI-351 c: 8-Planet System, 0.089 AU Out - [Made in Slatesource](https://slatesource.com/@steph/koi-351-c-8-planet-system-0-089-au-out) - By [Steph](https://slatesource.com/@steph) - Created on Sep 19, 2026 ## Terrestrial around KOI-351 It is 1.19 times Earth's radius, closest in size to Earth. A year there lasts 8.72 days, on an orbit 4 times closer to its star than Mercury is to the Sun. Its equilibrium temperature is 985 K (derived from the star rather than measured), hot enough to melt lead. 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 1.19 Earth radii Equilibrium temperature 985 K (derived) One year 8.72 days Orbit radius 0.0890 AU Host star KOI-351 at 6080 K Distance 2767 light-years Starlight blocked 0.008% at each transit What the transit gives How deep the star dims fixes the planet's size relative to it. 🔭🪐📅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 What has been measured here and what has not 0% A radius from transit photometry. Yes. A measured mass. No. A density, which decides rock or gas. No. An orbital distance. Yes. An observed temperature. No. The shape of the orbit. No. The archive lists no measured equilibrium temperature for this planet. The 985 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. Everything known here comes from how much light went missing. That fixes the size and leaves the mass entirely open. KOI-351 has 8 known planets. Multi-planet systems are where orbital dynamics can be measured rather than assumed. 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. # 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 [NASA Exoplanet Archive: every published measurement of this planet](https://exoplanetarchive.ipac.caltech.edu/overview/KOI-351%20c?utm_source=slatesource)