Kepler-397 b
Kepler-397 b is a mini-Neptune orbiting Kepler-397 in the constellation Cygnus. It was discovered in 2014 using the transit method.
How Big Is Kepler-397 b?
Kepler-397 b has a radius of 2.46 times that of Earth.
Is Kepler-397 b in the Habitable Zone?
Kepler-397 b orbits inside the inner edge of the habitable zone of Kepler-397. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of Kepler-397: 0.499–1.193 AU (conservative: 0.632–1.131 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-397 b — one full orbit around Kepler-397 — lasts 22.3 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.144 AU — closer to its star than Mercury is to the Sun.
How Was Kepler-397 b Discovered?
Kepler-397 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.
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-397 b scores 0.29, ranking #1,659 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: Kepler-397
Kepler-397
- Surface temperature
- 5,307 K (Sun: 5,772 K)
- Radius
- 0.77 R☉
The Kepler-397 Planetary System
Kepler-397 b is one of 2 known planets in the Kepler-397 system. Its siblings:
- Kepler-397 c (Cold Gas Giant)
Kepler-397 b — Complete Data
| Radius | 2.460 Earth radii (0.219 Jupiter radii) |
|---|---|
| Orbital period | 22.25 days |
| Orbital distance | 0.144 AU |
| Earth Similarity Index | 0.29 |
| Constellation | Cygnus |
| 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-397 b
Is Kepler-397 b habitable?
No — Kepler-397 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How big is Kepler-397 b compared to Earth?
Kepler-397 b has 2.46 times the radius of Earth.
How long is a year on Kepler-397 b?
One orbit around Kepler-397 takes 22.3 Earth days — short enough that 16 of its years would fit into one Earth year.
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