Kepler-129 b
Kepler-129 b is a super-Earth orbiting the G4 V star Kepler-129 in the constellation Draco. It lies about 1,334 light-years from Earth and was discovered in 2014 using the transit method.
How Big Is Kepler-129 b?
Kepler-129 b has a radius of 2.40 times that of Earth. Its mass is 20.0 times that of Earth, giving it a density of 8.10 g/cm³ — comparable to rocky planets like Earth (5.51 g/cm³).
Is Kepler-129 b in the Habitable Zone?
Kepler-129 b orbits inside the inner edge of the habitable zone of Kepler-129. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of Kepler-129: 1.238–2.917 AU (conservative: 1.568–2.765 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-129 b — one full orbit around Kepler-129 — lasts 15.8 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.130 AU — closer to its star than Mercury is to the Sun.
How Was Kepler-129 b Discovered?
Kepler-129 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-129 b?
Kepler-129 b is 1,333.5 light-years (408.8 parsecs) from Earth. Light arriving here tonight left the planet about 1,334 years ago. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 23,469,600 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-129 b scores 0.24, ranking #3,256 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: Kepler-129
Kepler-129
- Spectral type
- G4 V
- Surface temperature
- 5,770 K (Sun: 5,772 K)
- Mass
- 1.18 M☉
- Radius
- 1.65 R☉
- Age
- 6.4 billion years (Sun: 4.6)
The Kepler-129 Planetary System
Kepler-129 b is one of 3 known planets in the Kepler-129 system. Its siblings:
- Kepler-129 c (Super Earth)
- Kepler-129 d (Cold Gas Giant)
Kepler-129 b — Complete Data
| Radius | 2.400 Earth radii (0.214 Jupiter radii) |
|---|---|
| Mass (best estimate) | 20.00 Earth masses |
| Density | 8.10 g/cm³ (Earth: 5.51) |
| Orbital period | 15.79 days |
| Orbital distance | 0.130 AU |
| Earth Similarity Index | 0.24 |
| Distance from Earth | 1,333.5 light-years (408.8 parsecs) |
| Constellation | Draco |
| Discovery method | Transit |
| Discovery facility | Kepler |
| Discovery year | 2014 |
Data: NASA Exoplanet Archive, last updated 2021-06-28. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About Kepler-129 b
Is Kepler-129 b habitable?
No — Kepler-129 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is Kepler-129 b?
Kepler-129 b is about 1,334 light-years from Earth in the constellation Draco. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 23,469,600 years to get there.
How big is Kepler-129 b compared to Earth?
Kepler-129 b has 2.40 times the radius of Earth and about 20.0 times its mass.
How long is a year on Kepler-129 b?
One orbit around Kepler-129 takes 15.8 Earth days — short enough that 23 of its years would fit into one Earth year.
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