Kepler-22 b
Kepler-22 b is a super-Earth orbiting Kepler-22 in the constellation Cygnus. It lies about 635 light-years from Earth and was discovered in 2011 using the transit method. It orbits within the habitable zone of its star — the region where liquid water could exist on a planet's surface.
How Big Is Kepler-22 b?
Kepler-22 b has a radius of 2.10 times that of Earth. Its mass is 9.1 times that of Earth, giving it a density of 5.20 g/cm³ — comparable to rocky planets like Earth (5.51 g/cm³).
Is Kepler-22 b in the Habitable Zone?
Kepler-22 b orbits inside the conservative habitable zone of Kepler-22 — 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-22: 0.618–1.464 AU (conservative: 0.783–1.388 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 ›
Temperature on Kepler-22 b
The equilibrium temperature of Kepler-22 b is about 279 K (6 °C) — in a range broadly comparable to Earth, whose equilibrium temperature is 255 K. This estimate ignores any atmosphere, which could change surface temperatures dramatically — Earth's greenhouse effect adds about 33 °C. It receives 1.01 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on Kepler-22 b — one full orbit around Kepler-22 — lasts 289.9 Earth days, between the years of Mercury (88 days) and Earth (365 days). It orbits at an average distance of 0.812 AU — comparable to the inner Solar System. Its orbit is highly elliptical (eccentricity 0.72), swinging dramatically closer to and farther from its star.
How Was Kepler-22 b Discovered?
Kepler-22 b was discovered in 2011 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-22 b?
Kepler-22 b is 634.8 light-years (194.6 parsecs) from Earth. Light arriving here tonight left the planet around the year 1392. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 11,172,480 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-22 b scores 0.72, ranking #47 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: Kepler-22
Kepler-22
- Surface temperature
- 5,596 K (Sun: 5,772 K)
- Mass
- 0.86 M☉
- Radius
- 0.87 R☉
- Age
- 7.0 billion years (Sun: 4.6)
Planetary System
Kepler-22 b is the only planet known to orbit Kepler-22 so far.
Kepler-22 b — Complete Data
| Radius | 2.100 Earth radii (0.187 Jupiter radii) |
|---|---|
| Mass | 9.10 Earth masses (0.029 Jupiter masses) |
| Density | 5.20 g/cm³ (Earth: 5.51) |
| Orbital period | 289.86 days |
| Orbital distance | 0.812 AU |
| Eccentricity | 0.720 |
| Equilibrium temperature | 279 K (6 °C) |
| Stellar irradiation | 1.01× Earth |
| Earth Similarity Index | 0.72 |
| Distance from Earth | 634.8 light-years (194.6 parsecs) |
| Constellation | Cygnus |
| Discovery method | Transit |
| Discovery facility | Kepler |
| Discovery year | 2011 |
Data: NASA Exoplanet Archive, last updated 2023-04-17. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About Kepler-22 b
Is Kepler-22 b habitable?
Kepler-22 b orbits within the habitable zone of Kepler-22, 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-22 b?
Kepler-22 b is about 635 light-years from Earth in the constellation Cygnus. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 11,172,480 years to get there.
How big is Kepler-22 b compared to Earth?
Kepler-22 b has 2.10 times the radius of Earth and about 9.1 times its mass.
How long is a year on Kepler-22 b?
One orbit around Kepler-22 takes 289.9 Earth days.
Explore Kepler-22 b in the app
Browse, filter and compare 6,000+ exoplanets on iPhone, iPad and Apple Watch — with habitable-zone views, widgets and offline data.
