Kepler-308 c
Kepler-308 c is a mini-Neptune orbiting Kepler-308 in the constellation Cygnus. It lies about 4,357 light-years from Earth and was discovered in 2014 using the transit method.
How Big Is Kepler-308 c?
Kepler-308 c has a radius of 2.16 times that of Earth.
Is Kepler-308 c in the Habitable Zone?
Kepler-308 c orbits inside the inner edge of the habitable zone of Kepler-308. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of Kepler-308: 0.730–1.714 AU (conservative: 0.924–1.625 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
See the full interactive habitable-zone view in the Exoplanet Explorer app ›
Orbit and Year Length
A year on Kepler-308 c — one full orbit around Kepler-308 — lasts 15.4 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.123 AU — closer to its star than Mercury is to the Sun.
How Was Kepler-308 c Discovered?
Kepler-308 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-308 c?
Kepler-308 c is 4,357.2 light-years (1,335.9 parsecs) from Earth. Light arriving here tonight left the planet about 4,357 years ago. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 76,686,720 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-308 c scores 0.27, ranking #2,528 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: Kepler-308
Kepler-308
- Surface temperature
- 5,895 K (Sun: 5,772 K)
- Radius
- 0.94 R☉
The Kepler-308 Planetary System
Kepler-308 c is one of 2 known planets in the Kepler-308 system. Its siblings:
- Kepler-308 b (Mini Neptune)
Kepler-308 c — Complete Data
| Radius | 2.160 Earth radii (0.193 Jupiter radii) |
|---|---|
| Orbital period | 15.38 days |
| Orbital distance | 0.123 AU |
| Earth Similarity Index | 0.27 |
| Distance from Earth | 4,357.2 light-years (1,335.9 parsecs) |
| Constellation | Cygnus |
| Discovery method | Transit |
| Discovery facility | Kepler |
| Discovery year | 2014 |
Data: NASA Exoplanet Archive, last updated 2014-05-14. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About Kepler-308 c
Is Kepler-308 c habitable?
No — Kepler-308 c orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is Kepler-308 c?
Kepler-308 c is about 4,357 light-years from Earth in the constellation Cygnus. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 76,686,720 years to get there.
How big is Kepler-308 c compared to Earth?
Kepler-308 c has 2.16 times the radius of Earth.
How long is a year on Kepler-308 c?
One orbit around Kepler-308 takes 15.4 Earth days — short enough that 24 of its years would fit into one Earth year.
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