Kepler-109 c
Kepler-109 c is a mini-Neptune orbiting Kepler-109 in the constellation Lyra. It lies about 1,549 light-years from Earth and was discovered in 2014 using the transit method.
How Big Is Kepler-109 c?
Kepler-109 c has a radius of 2.65 times that of Earth. Its mass is 8.2 times that of Earth, giving it a density of 2.40 g/cm³ — between that of rocky and gaseous planets.
Is Kepler-109 c in the Habitable Zone?
Kepler-109 c orbits inside the inner edge of the habitable zone of Kepler-109. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of Kepler-109: 1.092–2.562 AU (conservative: 1.384–2.429 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on Kepler-109 c
The equilibrium temperature of Kepler-109 c is about 859 K (586 °C) — hot enough to melt many metals. This estimate ignores any atmosphere, which could change surface temperatures dramatically — Earth's greenhouse effect adds about 33 °C. It receives 91.00 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on Kepler-109 c — one full orbit around Kepler-109 — lasts 21.2 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.155 AU — closer to its star than Mercury is to the Sun. Its orbit is mildly elliptical (eccentricity 0.10).
How Was Kepler-109 c Discovered?
Kepler-109 c was discovered in 2014 using the transit method, with observations from Kepler.
The transit method watches a star for the tiny, regular dip in brightness that occurs when a planet crosses in front of it. The depth and timing of these dips reveal the planet's size and orbital period.
How Far Away Is Kepler-109 c?
Kepler-109 c is 1,548.8 light-years (474.9 parsecs) from Earth. Light arriving here tonight left the planet about 1,549 years ago. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 27,258,880 years to make the journey.
Earth Similarity Index
The Earth Similarity Index (ESI) scores how physically similar a planet is to Earth, from 0 to 1, based on radius, density, escape velocity and surface temperature. Kepler-109 c scores 0.24, ranking #3,368 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: Kepler-109
Kepler-109
- Surface temperature
- 5,950 K (Sun: 5,772 K)
- Mass
- 1.09 M☉
- Radius
- 1.39 R☉
- Age
- 6.2 billion years (Sun: 4.6)
The Kepler-109 Planetary System
Kepler-109 c is one of 2 known planets in the Kepler-109 system. Its siblings:
- Kepler-109 b (Mini Neptune)
Kepler-109 c — Complete Data
| Radius | 2.650 Earth radii (0.236 Jupiter radii) |
|---|---|
| Mass | 8.20 Earth masses (0.026 Jupiter masses) |
| Density | 2.40 g/cm³ (Earth: 5.51) |
| Orbital period | 21.22 days |
| Orbital distance | 0.155 AU |
| Eccentricity | 0.098 |
| Equilibrium temperature | 859 K (586 °C) |
| Stellar irradiation | 91.00× Earth |
| Earth Similarity Index | 0.24 |
| Distance from Earth | 1,548.8 light-years (474.9 parsecs) |
| Constellation | Lyra |
| Discovery method | Transit |
| Discovery facility | Kepler |
| Discovery year | 2014 |
Data: NASA Exoplanet Archive, last updated 2023-04-17. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About Kepler-109 c
Is Kepler-109 c habitable?
No — Kepler-109 c orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is Kepler-109 c?
Kepler-109 c is about 1,549 light-years from Earth in the constellation Lyra. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 27,258,880 years to get there.
How big is Kepler-109 c compared to Earth?
Kepler-109 c has 2.65 times the radius of Earth and about 8.2 times its mass.
How long is a year on Kepler-109 c?
One orbit around Kepler-109 takes 21.2 Earth days — short enough that 17 of its years would fit into one Earth year.
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