Kepler-102 e
Kepler-102 e is a mini-Neptune orbiting Kepler-102 in the constellation Lyra. It lies about 352 light-years from Earth and was discovered in 2013 using the transit method.
How Big Is Kepler-102 e?
Kepler-102 e has a radius of 2.17 times that of Earth. Its mass is 4.7 times that of Earth, giving it a density of 2.50 g/cm³ — between that of rocky and gaseous planets.
Is Kepler-102 e in the Habitable Zone?
Kepler-102 e orbits inside the inner edge of the habitable zone of Kepler-102. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of Kepler-102: 0.411–0.998 AU (conservative: 0.521–0.946 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on Kepler-102 e
The equilibrium temperature of Kepler-102 e is about 590 K (317 °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 20.30 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on Kepler-102 e — one full orbit around Kepler-102 — lasts 16.1 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.116 AU — closer to its star than Mercury is to the Sun. Its orbit is mildly elliptical (eccentricity 0.09).
How Was Kepler-102 e Discovered?
Kepler-102 e was discovered in 2013 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-102 e?
Kepler-102 e is 351.6 light-years (107.8 parsecs) from Earth. Light arriving here tonight left the planet around the year 1675. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 6,188,160 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-102 e scores 0.31, ranking #1,134 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: Kepler-102
Kepler-102
- Surface temperature
- 4,909 K (Sun: 5,772 K)
- Mass
- 0.80 M☉
- Radius
- 0.72 R☉
- Age
- 1.1 billion years (Sun: 4.6)
The Kepler-102 Planetary System
Kepler-102 e is one of 5 known planets in the Kepler-102 system. Its siblings:
- Kepler-102 b (Terrestrial)
- Kepler-102 c (Terrestrial)
- Kepler-102 d (Terrestrial)
- Kepler-102 f (Terrestrial)
Kepler-102 e — Complete Data
| Radius | 2.170 Earth radii (0.194 Jupiter radii) |
|---|---|
| Mass | 4.70 Earth masses (0.015 Jupiter masses) |
| Density | 2.50 g/cm³ (Earth: 5.51) |
| Orbital period | 16.15 days |
| Orbital distance | 0.116 AU |
| Eccentricity | 0.089 |
| Equilibrium temperature | 590 K (317 °C) |
| Stellar irradiation | 20.30× Earth |
| Earth Similarity Index | 0.31 |
| Distance from Earth | 351.6 light-years (107.8 parsecs) |
| Constellation | Lyra |
| Discovery method | Transit |
| Discovery facility | Kepler |
| Discovery year | 2013 |
Data: NASA Exoplanet Archive, last updated 2023-04-17. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About Kepler-102 e
Is Kepler-102 e habitable?
No — Kepler-102 e orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is Kepler-102 e?
Kepler-102 e is about 352 light-years from Earth in the constellation Lyra. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 6,188,160 years to get there.
How big is Kepler-102 e compared to Earth?
Kepler-102 e has 2.17 times the radius of Earth and about 4.7 times its mass.
How long is a year on Kepler-102 e?
One orbit around Kepler-102 takes 16.1 Earth days — short enough that 23 of its years would fit into one Earth year.
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