Kepler-421 b
Kepler-421 b is a Neptune-like planet orbiting the G9/K0 star Kepler-421 in the constellation Lyra. It lies about 1,137 light-years from Earth and was discovered in 2014 using the transit method.
How Big Is Kepler-421 b?
Kepler-421 b has a radius of 4.16 times that of Earth.
Is Kepler-421 b in the Habitable Zone?
Kepler-421 b orbits beyond the outer edge of the habitable zone of Kepler-421. At that distance, any surface water would almost certainly be frozen.
Habitable zone of Kepler-421: 0.488–1.165 AU (conservative: 0.618–1.105 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-421 b
The equilibrium temperature of Kepler-421 b is about 185 K (-88 °C) — well below freezing. This estimate ignores any atmosphere, which could change surface temperatures dramatically — Earth's greenhouse effect adds about 33 °C.
Orbit and Year Length
A year on Kepler-421 b — one full orbit around Kepler-421 — lasts 704.2 Earth days, longer than an Earth year. It orbits at an average distance of 1.219 AU. Its orbit is nearly circular (eccentricity 0.041).
How Was Kepler-421 b Discovered?
Kepler-421 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-421 b?
Kepler-421 b is 1,136.8 light-years (348.6 parsecs) from Earth. Light arriving here tonight left the planet about 1,137 years ago. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 20,007,680 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-421 b scores 0.41, ranking #447 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: Kepler-421
Kepler-421
- Spectral type
- G9/K0
- Surface temperature
- 5,308 K (Sun: 5,772 K)
- Mass
- 0.79 M☉
- Radius
- 0.76 R☉
- Luminosity
- 0.3999 L☉
- Age
- 4.0 billion years (Sun: 4.6)
Planetary System
Kepler-421 b is the only planet known to orbit Kepler-421 so far.
Kepler-421 b — Complete Data
| Radius | 4.160 Earth radii (0.371 Jupiter radii) |
|---|---|
| Orbital period | 704.20 days |
| Orbital distance | 1.219 AU |
| Eccentricity | 0.041 |
| Equilibrium temperature | 185 K (-88 °C) |
| Earth Similarity Index | 0.41 |
| Distance from Earth | 1,136.8 light-years (348.6 parsecs) |
| Constellation | Lyra |
| Discovery method | Transit |
| Discovery facility | Kepler |
| Discovery year | 2014 |
Data: NASA Exoplanet Archive, last updated 2014-07-23. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About Kepler-421 b
Is Kepler-421 b habitable?
No — Kepler-421 b orbits outside the habitable zone of Kepler-421 and is likely too cold for liquid water on its surface.
How far away is Kepler-421 b?
Kepler-421 b is about 1,137 light-years from Earth in the constellation Lyra. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 20,007,680 years to get there.
How big is Kepler-421 b compared to Earth?
Kepler-421 b has 4.16 times the radius of Earth.
How long is a year on Kepler-421 b?
One orbit around Kepler-421 takes 704.2 Earth days.
Explore Kepler-421 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.
