Kepler-538 b
Kepler-538 b is a super-Earth orbiting Kepler-538 in the constellation Cygnus. It lies about 509 light-years from Earth and was discovered in 2016 using the transit method.
How Big Is Kepler-538 b?
Kepler-538 b has a radius of 2.22 times that of Earth. Its mass is 12.9 times that of Earth, giving it a density of 6.50 g/cm³ — comparable to rocky planets like Earth (5.51 g/cm³).
Is Kepler-538 b in the Habitable Zone?
Kepler-538 b orbits inside the inner edge of the habitable zone of Kepler-538. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of Kepler-538: 0.609–1.444 AU (conservative: 0.771–1.369 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on Kepler-538 b
The equilibrium temperature of Kepler-538 b is about 417 K (144 °C) — hotter than anywhere on Earth. This estimate ignores any atmosphere, which could change surface temperatures dramatically — Earth's greenhouse effect adds about 33 °C. It receives 5.07 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on Kepler-538 b — one full orbit around Kepler-538 — lasts 81.7 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.355 AU — closer to its star than Mercury is to the Sun. Its orbit is mildly elliptical (eccentricity 0.21).
How Was Kepler-538 b Discovered?
Kepler-538 b was discovered in 2016 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-538 b?
Kepler-538 b is 508.7 light-years (156.0 parsecs) from Earth. Light arriving here tonight left the planet around the year 1518. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 8,953,120 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-538 b scores 0.45, ranking #345 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: Kepler-538
Kepler-538 b belongs to a system of 2 stars; it orbits Kepler-538.
Kepler-538
- Surface temperature
- 5,534 K (Sun: 5,772 K)
- Mass
- 0.89 M☉
- Radius
- 0.87 R☉
- Age
- 5.3 billion years (Sun: 4.6)
Planetary System
Kepler-538 b is the only planet known to orbit Kepler-538 so far.
Kepler-538 b — Complete Data
| Radius | 2.215 Earth radii (0.198 Jupiter radii) |
|---|---|
| Mass | 12.90 Earth masses (0.041 Jupiter masses) |
| Density | 6.50 g/cm³ (Earth: 5.51) |
| Orbital period | 81.74 days |
| Orbital distance | 0.355 AU |
| Eccentricity | 0.210 |
| Equilibrium temperature | 417 K (144 °C) |
| Stellar irradiation | 5.07× Earth |
| Earth Similarity Index | 0.45 |
| Distance from Earth | 508.7 light-years (156.0 parsecs) |
| Constellation | Cygnus |
| Discovery method | Transit |
| Discovery facility | Kepler |
| Discovery year | 2016 |
Data: NASA Exoplanet Archive, last updated 2023-04-17. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About Kepler-538 b
Is Kepler-538 b habitable?
No — Kepler-538 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is Kepler-538 b?
Kepler-538 b is about 509 light-years from Earth in the constellation Cygnus. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 8,953,120 years to get there.
How big is Kepler-538 b compared to Earth?
Kepler-538 b has 2.22 times the radius of Earth and about 12.9 times its mass.
How long is a year on Kepler-538 b?
One orbit around Kepler-538 takes 81.7 Earth days.
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