Kepler-129 d
Kepler-129 d is a cold gas giant orbiting the G4 V star Kepler-129 in the constellation Draco. It lies about 1,334 light-years from Earth and was discovered in 2021 using the radial velocity method.
Is Kepler-129 d in the Habitable Zone?
Kepler-129 d orbits beyond the outer edge of the habitable zone of Kepler-129. At that distance, any surface water would almost certainly be frozen.
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 d — one full orbit around Kepler-129 — lasts 2,646.0 Earth days, longer than an Earth year. It orbits at an average distance of 4.000 AU. Its orbit is mildly elliptical (eccentricity 0.15).
How Was Kepler-129 d Discovered?
Kepler-129 d was discovered in 2021 using the radial velocity method, with observations from W. M. Keck Observatory.
The radial velocity method measures the subtle wobble of a star caused by the gravitational pull of an orbiting planet, visible as periodic shifts in the star's light spectrum. The size of the wobble reveals the planet's minimum mass.
How Far Away Is Kepler-129 d?
Kepler-129 d 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 d scores 0.22, ranking #3,626 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 d is one of 3 known planets in the Kepler-129 system. Its siblings:
- Kepler-129 b (Super Earth)
- Kepler-129 c (Super Earth)
Kepler-129 d — Complete Data
| Mass (best estimate) | 2,637.98 Earth masses |
|---|---|
| Orbital period | 2,646.00 days |
| Orbital distance | 4.000 AU |
| Eccentricity | 0.150 |
| Earth Similarity Index | 0.22 |
| Distance from Earth | 1,333.5 light-years (408.8 parsecs) |
| Constellation | Draco |
| Discovery method | Radial Velocity |
| Discovery facility | W. M. Keck Observatory |
| Discovery year | 2021 |
Data: NASA Exoplanet Archive, last updated 2021-06-28. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About Kepler-129 d
Is Kepler-129 d habitable?
No — Kepler-129 d orbits outside the habitable zone of Kepler-129 and is likely too cold for liquid water on its surface.
How far away is Kepler-129 d?
Kepler-129 d 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 long is a year on Kepler-129 d?
One orbit around Kepler-129 takes 2,646.0 Earth days.
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