Kepler-425 b
Kepler-425 b is a hot Jupiter orbiting the K1 V star Kepler-425 in the constellation Lyra. It lies about 2,109 light-years from Earth and was discovered in 2014 using the transit method.
How Big Is Kepler-425 b?
Kepler-425 b has a radius of 10.96 times that of Earth, or 0.98 times the radius of Jupiter. Its mass is 79.5 times that of Earth, giving it a density of 0.27 g/cm³ — closer to gas planets like Jupiter (1.33 g/cm³).
Is Kepler-425 b in the Habitable Zone?
Kepler-425 b orbits inside the inner edge of the habitable zone of Kepler-425. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of Kepler-425: 0.535–1.286 AU (conservative: 0.678–1.219 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on Kepler-425 b
The equilibrium temperature of Kepler-425 b is about 1,070 K (797 °C) — hot enough to melt many metals. 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-425 b — one full orbit around Kepler-425 — lasts 3.80 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.046 AU — closer to its star than Mercury is to the Sun. Its orbit is highly elliptical (eccentricity 0.33), swinging dramatically closer to and farther from its star.
How Was Kepler-425 b Discovered?
Kepler-425 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.
How Far Away Is Kepler-425 b?
Kepler-425 b is 2,109.1 light-years (646.6 parsecs) from Earth. Light arriving here tonight left the planet about 2,109 years ago. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 37,120,160 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-425 b scores 0.08, ranking #4,586 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: Kepler-425
Kepler-425
- Spectral type
- K1 V
- Surface temperature
- 5,170 K (Sun: 5,772 K)
- Mass
- 0.93 M☉
- Radius
- 0.86 R☉
- Luminosity
- 0.4753 L☉
- Age
- 5.0 billion years (Sun: 4.6)
Planetary System
Kepler-425 b is the only planet known to orbit Kepler-425 so far.
Kepler-425 b — Complete Data
| Radius | 10.962 Earth radii (0.978 Jupiter radii) |
|---|---|
| Mass | 79.45 Earth masses (0.250 Jupiter masses) |
| Density | 0.27 g/cm³ (Earth: 5.51) |
| Orbital period | 3.80 days |
| Orbital distance | 0.046 AU |
| Eccentricity | 0.330 |
| Equilibrium temperature | 1,070 K (797 °C) |
| Earth Similarity Index | 0.08 |
| Distance from Earth | 2,109.1 light-years (646.6 parsecs) |
| Constellation | Lyra |
| Discovery method | Transit |
| Discovery facility | Kepler |
| Discovery year | 2014 |
Data: NASA Exoplanet Archive, last updated 2014-10-03. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About Kepler-425 b
Is Kepler-425 b habitable?
No — Kepler-425 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is Kepler-425 b?
Kepler-425 b is about 2,109 light-years from Earth in the constellation Lyra. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 37,120,160 years to get there.
How big is Kepler-425 b compared to Earth?
Kepler-425 b has 10.96 times the radius of Earth and about 79.5 times its mass.
How long is a year on Kepler-425 b?
One orbit around Kepler-425 takes 3.8 Earth days — short enough that 96 of its years would fit into one Earth year.
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