Kepler-103 c
Kepler-103 c is a Neptune-like planet orbiting the G2 star Kepler-103 in the constellation Lyra. It lies about 1,614 light-years from Earth and was discovered in 2014 using the transit method.
How Big Is Kepler-103 c?
Kepler-103 c has a radius of 5.45 times that of Earth. Its mass is 58.5 times that of Earth, giving it a density of 1.98 g/cm³ — closer to gas planets like Jupiter (1.33 g/cm³).
Is Kepler-103 c in the Habitable Zone?
Kepler-103 c orbits inside the inner edge of the habitable zone of Kepler-103. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of Kepler-103: 1.206–2.824 AU (conservative: 1.528–2.677 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-103 c — one full orbit around Kepler-103 — lasts 179.6 Earth days, between the years of Mercury (88 days) and Earth (365 days). It orbits at an average distance of 0.668 AU — comparable to the inner Solar System. Its orbit is mildly elliptical (eccentricity 0.10).
How Was Kepler-103 c Discovered?
Kepler-103 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-103 c?
Kepler-103 c is 1,613.9 light-years (494.8 parsecs) from Earth. Light arriving here tonight left the planet about 1,614 years ago. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 28,404,640 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-103 c scores 0.30, ranking #1,481 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: Kepler-103
Kepler-103
- Spectral type
- G2
- Surface temperature
- 6,047 K (Sun: 5,772 K)
- Mass
- 1.21 M☉
- Radius
- 1.49 R☉
The Kepler-103 Planetary System
Kepler-103 c is one of 2 known planets in the Kepler-103 system. Its siblings:
- Kepler-103 b (Sub Neptune)
Kepler-103 c — Complete Data
| Radius | 5.454 Earth radii (0.487 Jupiter radii) |
|---|---|
| Mass | 58.47 Earth masses (0.184 Jupiter masses) |
| Density | 1.98 g/cm³ (Earth: 5.51) |
| Orbital period | 179.61 days |
| Orbital distance | 0.668 AU |
| Eccentricity | 0.103 |
| Earth Similarity Index | 0.30 |
| Distance from Earth | 1,613.9 light-years (494.8 parsecs) |
| Constellation | Lyra |
| Discovery method | Transit |
| Discovery facility | Kepler |
| Discovery year | 2014 |
Data: NASA Exoplanet Archive, last updated 2025-09-17. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About Kepler-103 c
Is Kepler-103 c habitable?
No — Kepler-103 c orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is Kepler-103 c?
Kepler-103 c is about 1,614 light-years from Earth in the constellation Lyra. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 28,404,640 years to get there.
How big is Kepler-103 c compared to Earth?
Kepler-103 c has 5.45 times the radius of Earth and about 58.5 times its mass.
How long is a year on Kepler-103 c?
One orbit around Kepler-103 takes 179.6 Earth days.
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