Kepler-103 b
Kepler-103 b is a sub-Neptune 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 b?
Kepler-103 b has a radius of 3.49 times that of Earth. Its mass is 11.7 times that of Earth, giving it a density of 1.52 g/cm³ — closer to gas planets like Jupiter (1.33 g/cm³).
Is Kepler-103 b in the Habitable Zone?
Kepler-103 b 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 b — one full orbit around Kepler-103 — lasts 16.0 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.133 AU — closer to its star than Mercury is to the Sun. Its orbit is mildly elliptical (eccentricity 0.17).
How Was Kepler-103 b Discovered?
Kepler-103 b 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 b?
Kepler-103 b 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 b scores 0.20, ranking #3,884 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 b is one of 2 known planets in the Kepler-103 system. Its siblings:
- Kepler-103 c (Neptune-like)
Kepler-103 b — Complete Data
| Radius | 3.486 Earth radii (0.311 Jupiter radii) |
|---|---|
| Mass | 11.67 Earth masses (0.037 Jupiter masses) |
| Density | 1.52 g/cm³ (Earth: 5.51) |
| Orbital period | 15.97 days |
| Orbital distance | 0.133 AU |
| Eccentricity | 0.171 |
| Earth Similarity Index | 0.20 |
| 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 b
Is Kepler-103 b habitable?
No — Kepler-103 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is Kepler-103 b?
Kepler-103 b 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 b compared to Earth?
Kepler-103 b has 3.49 times the radius of Earth and about 11.7 times its mass.
How long is a year on Kepler-103 b?
One orbit around Kepler-103 takes 16.0 Earth days — short enough that 23 of its years would fit into one Earth year.
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