---
title: "The Kepler-309 system"
url: "https://spacecatalog.org/system/kepler-309"
release: "DR1"
licence: "No licence stated; acknowledgement requested"
citation: "This research has made use of the NASA Exoplanet Archive, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program. Cite Christiansen et al. (2025), Planetary Science Journal (doi:10.3847/PSJ/ade3c2), and the literature reference given with each value."
---

# The Kepler-309 system

Kepler-309 is an M0 V red star in Cygnus, 1776 ly away, with 2 known planets. Their orbits run from 0.0590 to 0.401 AU. All of them were detected by transit.

## The planets, innermost first

| Planet | Orbit (AU) | Period | Radius | Mass | Equilibrium T |
| --- | --- | --- | --- | --- | --- |
| [b](https://spacecatalog.org/object/kepler-309-b) | 0.0590 | 5.924 d | 1.56 R⊕ | 3.05 M⊕ | 531 K |
| [c](https://spacecatalog.org/object/kepler-309-c) | 0.401 | 105.4 d | 2.51 R⊕ | 6.85 M⊕ | 204 K |

Every figure is the planet's composite parameter from the [NASA Exoplanet Archive (Planetary Systems Composite Parameters)](https://exoplanetarchive.ipac.caltech.edu/cgi-bin/TblView/nph-tblView?app=ExoTbls&config=PSCompPars), one consistent set per world. Semi-major axes are orbits about the star, not distances from Earth.

This research has made use of the NASA Exoplanet Archive, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program. Cite Christiansen et al. (2025), Planetary Science Journal (doi:10.3847/PSJ/ade3c2), and the literature reference given with each value.

## The host star

| Quantity | Value |
| --- | --- |
| CLASS | M0 V red star |
| SPECTRAL TYPE | M0 V |
| MASS | 0.816 M☉ |
| RADIUS | 0.721 R☉ |
| SURFACE TEMPERATURE | 4713 K |
| LUMINOSITY | 0.231 L☉ |
| DISTANCE FROM EARTH | 1776 ly |
| APPARENT MAGNITUDE | 15.42 |
| CONSTELLATION | Cygnus |
| STARS IN SYSTEM | 1 |

The star itself: https://spacecatalog.org/object/kepler-309

The page itself, with the orbits drawn: https://spacecatalog.org/system/kepler-309