Kepler-438 b
Kepler-438 b is a terrestrial planet orbiting Kepler-438 in the constellation Lyra. It lies about 639 light-years from Earth and was discovered in 2015 using the transit method.
How Big Is Kepler-438 b?
Kepler-438 b has a radius of 1.12 times that of Earth.
Is Kepler-438 b in the Habitable Zone?
Kepler-438 b orbits inside the inner edge of the habitable zone of Kepler-438. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of Kepler-438: 0.171–0.438 AU (conservative: 0.216–0.415 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on Kepler-438 b
Kepler-438 b receives 1.40 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on Kepler-438 b — one full orbit around Kepler-438 — lasts 35.2 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.166 AU — closer to its star than Mercury is to the Sun. Its orbit is nearly circular (eccentricity 0.030).
How Was Kepler-438 b Discovered?
Kepler-438 b was discovered in 2015 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-438 b?
Kepler-438 b is 639.1 light-years (195.9 parsecs) from Earth. Light arriving here tonight left the planet around the year 1387. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 11,248,160 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-438 b scores 0.83, ranking #18 of 5,565 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: Kepler-438
Kepler-438
- Surface temperature
- 3,748 K (Sun: 5,772 K)
- Mass
- 0.54 M☉
- Radius
- 0.52 R☉
- Luminosity
- 0.0440 L☉
- Age
- 4.4 billion years (Sun: 4.6)
Planetary System
Kepler-438 b is the only planet known to orbit Kepler-438 so far.
Kepler-438 b — Complete Data
| Radius | 1.120 Earth radii (0.100 Jupiter radii) |
|---|---|
| Orbital period | 35.23 days |
| Orbital distance | 0.166 AU |
| Eccentricity | 0.030 |
| Stellar irradiation | 1.40× Earth |
| Earth Similarity Index | 0.83 |
| Distance from Earth | 639.1 light-years (195.9 parsecs) |
| Constellation | Lyra |
| Discovery method | Transit |
| Discovery facility | Kepler |
| Discovery year | 2015 |
Data: NASA Exoplanet Archive, last updated 2015-01-06. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About Kepler-438 b
Is Kepler-438 b habitable?
No — Kepler-438 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is Kepler-438 b?
Kepler-438 b is about 639 light-years from Earth in the constellation Lyra. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 11,248,160 years to get there.
How big is Kepler-438 b compared to Earth?
Kepler-438 b has 1.12 times the radius of Earth.
How long is a year on Kepler-438 b?
One orbit around Kepler-438 takes 35.2 Earth days — short enough that 10 of its years would fit into one Earth year.
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