Gas Giant

Kepler-9 c

Orbiting Kepler-9 | 628.3 parsecs away

Kepler-9 c is a Gas Giant exoplanet (a massive planet composed primarily of hydrogen and helium), about 8.1 times the radius of Earth. The planet completes one orbit around its star every 39.0 Earth days. It was discovered in 2010 using the transit method. It orbits the star Kepler-9, located approximately 628 parsecs (2049 light-years) from Earth.

More Gas Giant planets →Transit method →

2010

Discovered

29.9

Earth Masses

8.08

Earth Radii

Discovery Information

Discovery MethodTransit

Discovery Year2,010

Discovery FacilityKepler

Orbital Properties

Orbital Period38.9853 days

Semi-Major Axis0.227 AU

Eccentricity0.0669

Inclination89.188 deg

Physical Properties

Mass (Jupiter)0.0941 MJ

Mass (Earth)29.9 M⊕

Radius (Jupiter)0.7208 RJ

Radius (Earth)8.08 R⊕

Density0.31 g/cm3

Planetary Extremes

Where Kepler-9 c sits on the spectrum of all known exoplanets.

Mass29.9 M⊕

FeatherweightColossus

Radius8.08 R⊕

TinyEnormous

Year Length39.0 days

LightningGlacial

Density0.31 g/cm³

FluffyIron-dense

Star Distance0.227 AU

ScorchedFrozen exile

Star System View

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Size Comparison

8.08x Earth's radius (0.72x Jupiter)

Orbit Comparison

Earth: 365.25 days (1 AU)Kepler-9 c: 39.0 Earth days (0.227 AU)

Host Star: Kepler-9

Effective Temperature5,774 K

Mass1.022 M☉

Radius0.958 R☉

Size vs Sun1.04x smaller

Luminosity0.9162 L☉

Luminosity vs Sun1.1x dimmer

Metallicity [Fe/H]0.05

Distance (pc)628.257 pc

Distance (ly)2049.1 light-years

Planets in the Kepler-9 System

Kepler-9 dSuper-Earth

0.027 AU1.6 d

Kepler-9 bGas Giant

0.143 AU19.2 d

Kepler-9 cGas Giant(viewing)

0.227 AU39.0 d

What If You Lived Here?

32.1 kg

Your weight (from 70 kg)

0.46g

Feather-light

Walking feels like bounding on a trampoline.

39.0 Earth days

Year length

Unknown sunrise

View on NASA Archive Compare with Other Planets

Test Your Knowledge

Related Research

DetectionApr 10, 2026

The Illusory Precision of TTV Masses: Hidden Solutions Behind Kepler-9's Tight Mass Ratio

Sheng Jin, Dong-Hong Wu, Xiao-Ling Xu et al.

Transit timing variations (TTV) are considered a tool for constraining the masses of transiting planets in the absence of radial-velocity data. Although theoretical studies have long revealed that TTV...

AtmospheresJul 18, 2025

Updated Masses for the Gas Giants in the Eight-Planet Kepler-90 System Via Transit-Timing Variation and Radial Velocity Observations

David E. Shaw, Lauren M. Weiss, Eric Agol et al.

The eight-planet Kepler-90 system exhibits the greatest multiplicity of planets found to date. All eight planets are transiting and were discovered in photometry from the NASA Kepler primary mission. ...

DetectionJun 12, 2025

The Gap-Giant Association: Are Planets Hiding in the Gaps?

Caleb Lammers, Joshua N. Winn

A handful of stars are known to host both an inner system of multiple transiting planets and an outer giant planet. These systems all feature a prominent gap between the orbits of two of the transitin...

DetectionJul 18, 2022

TESS Observations of Kepler systems with Transit Timing Variations

Daniel Jontof-Hutter, Paul A. Dalba, John H. Livingston

We identify targets in the Kepler field that may be characterized by transit timing variations (TTVs) and are detectable by the Transiting Exoplanet Survey Satellite (TESS). Despite the reduced signal...

HabitabilityNov 25, 2021

Kepler-93: a testbed for detailed seismic modelling and orbital evolution of super-earths around solar-like stars

J. Bétrisey, C. Pezzotti, G. Buldgen et al.

The advent of space-based photometry missions such as CoRoT, Kepler and TESS has sparkled the development of asteroseismology and exoplanetology. The advent of PLATO will further strengthen such multi...

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