Kepler-68 d
Kepler-68 d is a cold gas giant orbiting Kepler-68 in the constellation Cygnus. It lies about 470 light-years from Earth and was discovered in 2013 using the radial velocity method. It orbits within the habitable zone of its star — the region where liquid water could exist on a planet's surface.
Is Kepler-68 d in the Habitable Zone?
Kepler-68 d orbits inside the conservative habitable zone of Kepler-68 — the region where a rocky planet could sustain liquid water on its surface. This makes it one of the most interesting known exoplanets in the search for life.
Habitable zone of Kepler-68: 0.962–2.261 AU (conservative: 1.218–2.144 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-68 d — one full orbit around Kepler-68 — lasts 632.6 Earth days, longer than an Earth year. It orbits at an average distance of 1.469 AU. Its orbit is mildly elliptical (eccentricity 0.10).
How Was Kepler-68 d Discovered?
Kepler-68 d was discovered in 2013 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-68 d?
Kepler-68 d is 470.2 light-years (144.2 parsecs) from Earth. Light arriving here tonight left the planet around the year 1556. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 8,275,520 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-68 d scores 0.38, ranking #561 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: Kepler-68
Kepler-68 d belongs to a system of 2 stars; it orbits Kepler-68.
Kepler-68
- Surface temperature
- 5,847 K (Sun: 5,772 K)
- Mass
- 1.06 M☉
- Radius
- 1.26 R☉
- Age
- 6.8 billion years (Sun: 4.6)
The Kepler-68 Planetary System
Kepler-68 d is one of 4 known planets in the Kepler-68 system. Its siblings:
- Kepler-68 b (Super Earth)
- Kepler-68 c (Terrestrial)
- Kepler-68 e (Cold Gas Giant)
Kepler-68 d — Complete Data
| Mass (best estimate) | 238.05 Earth masses |
|---|---|
| Orbital period | 632.62 days |
| Orbital distance | 1.469 AU |
| Eccentricity | 0.102 |
| Earth Similarity Index | 0.38 |
| Distance from Earth | 470.2 light-years (144.2 parsecs) |
| Constellation | Cygnus |
| Discovery method | Radial Velocity |
| Discovery facility | W. M. Keck Observatory |
| Discovery year | 2013 |
Data: NASA Exoplanet Archive, last updated 2023-04-17. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About Kepler-68 d
Is Kepler-68 d habitable?
Kepler-68 d orbits within the habitable zone of Kepler-68, the region where liquid water could exist on a planet's surface. It sits in the conservative habitable zone — the most promising region for habitability. Whether it is actually habitable depends on its atmosphere and composition, which remain unknown.
How far away is Kepler-68 d?
Kepler-68 d is about 470 light-years from Earth in the constellation Cygnus. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 8,275,520 years to get there.
How long is a year on Kepler-68 d?
One orbit around Kepler-68 takes 632.6 Earth days.
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