Kepler-222 d
Kepler-222 d is a sub-Neptune orbiting Kepler-222 in the constellation Lyra. It lies about 2,475 light-years from Earth and was discovered in 2014 using the transit method.
How Big Is Kepler-222 d?
Kepler-222 d has a radius of 3.69 times that of Earth.
Is Kepler-222 d in the Habitable Zone?
Kepler-222 d orbits inside the inner edge of the habitable zone of Kepler-222. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of Kepler-222: 0.588–1.400 AU (conservative: 0.745–1.328 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-222 d — one full orbit around Kepler-222 — lasts 28.1 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.180 AU — closer to its star than Mercury is to the Sun.
How Was Kepler-222 d Discovered?
Kepler-222 d 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-222 d?
Kepler-222 d is 2,475.0 light-years (758.9 parsecs) from Earth. Light arriving here tonight left the planet about 2,475 years ago. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 43,560,000 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-222 d scores 0.26, ranking #2,751 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: Kepler-222
Kepler-222
- Surface temperature
- 5,433 K (Sun: 5,772 K)
- Radius
- 0.87 R☉
The Kepler-222 Planetary System
Kepler-222 d is one of 3 known planets in the Kepler-222 system. Its siblings:
- Kepler-222 b (Sub Neptune)
- Kepler-222 c (Neptune-like)
Kepler-222 d — Complete Data
| Radius | 3.690 Earth radii (0.329 Jupiter radii) |
|---|---|
| Orbital period | 28.08 days |
| Orbital distance | 0.180 AU |
| Earth Similarity Index | 0.26 |
| Distance from Earth | 2,475.0 light-years (758.9 parsecs) |
| Constellation | Lyra |
| Discovery method | Transit |
| Discovery facility | Kepler |
| Discovery year | 2014 |
Data: NASA Exoplanet Archive, last updated 2014-05-14. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About Kepler-222 d
Is Kepler-222 d habitable?
No — Kepler-222 d orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is Kepler-222 d?
Kepler-222 d is about 2,475 light-years from Earth in the constellation Lyra. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 43,560,000 years to get there.
How big is Kepler-222 d compared to Earth?
Kepler-222 d has 3.69 times the radius of Earth.
How long is a year on Kepler-222 d?
One orbit around Kepler-222 takes 28.1 Earth days — short enough that 13 of its years would fit into one Earth year.
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