Kepler-38 b
Kepler-38 b is a Neptune-like planet orbiting the G4 V star Kepler-38 in the constellation Lyra. It lies about 3,831 light-years from Earth and was discovered in 2012 using the transit method.
How Big Is Kepler-38 b?
Kepler-38 b has a radius of 4.30 times that of Earth. Its mass is 122 times that of Earth.
Is Kepler-38 b in the Habitable Zone?
Kepler-38 b orbits inside the inner edge of the habitable zone of Kepler-38. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of Kepler-38: 1.257–2.974 AU (conservative: 1.592–2.819 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on Kepler-38 b
The equilibrium temperature of Kepler-38 b is about 475 K (202 °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.
Orbit and Year Length
A year on Kepler-38 b — one full orbit around Kepler-38 — lasts 105.6 Earth days, between the years of Mercury (88 days) and Earth (365 days). It orbits at an average distance of 0.463 AU — comparable to the inner Solar System. Its orbit is nearly circular (eccentricity 0.032).
How Was Kepler-38 b Discovered?
Kepler-38 b was discovered in 2012 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-38 b?
Kepler-38 b is 3,831.0 light-years (1,174.6 parsecs) from Earth. Light arriving here tonight left the planet about 3,831 years ago. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 67,425,600 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-38 b scores 0.24, ranking #3,251 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: Kepler-38
Kepler-38 b is a circumbinary planet — it orbits around two stars at once, like Tatooine in Star Wars.
Kepler-38
- Spectral type
- G4 V
- Surface temperature
- 5,623 K (Sun: 5,772 K)
- Mass
- 0.94 M☉
- Radius
- 1.75 R☉
- Age
- 10.0 billion years (Sun: 4.6)
Planetary System
Kepler-38 b is the only planet known to orbit Kepler-38 so far.
Kepler-38 b — Complete Data
| Radius | 4.300 Earth radii (0.384 Jupiter radii) |
|---|---|
| Mass | 122.00 Earth masses (0.384 Jupiter masses) |
| Orbital period | 105.60 days |
| Orbital distance | 0.463 AU |
| Eccentricity | 0.032 |
| Equilibrium temperature | 475 K (202 °C) |
| Earth Similarity Index | 0.24 |
| Distance from Earth | 3,831.0 light-years (1,174.6 parsecs) |
| Constellation | Lyra |
| Discovery method | Transit |
| Discovery facility | Kepler |
| Discovery year | 2012 |
Data: NASA Exoplanet Archive, last updated 2014-05-14. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About Kepler-38 b
Is Kepler-38 b habitable?
No — Kepler-38 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is Kepler-38 b?
Kepler-38 b is about 3,831 light-years from Earth in the constellation Lyra. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 67,425,600 years to get there.
How big is Kepler-38 b compared to Earth?
Kepler-38 b has 4.30 times the radius of Earth and about 122 times its mass.
How long is a year on Kepler-38 b?
One orbit around Kepler-38 takes 105.6 Earth days.
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