Kepler-12 b
Kepler-12 b is a hot Jupiter orbiting Kepler-12 in the constellation Draco. It lies about 2,875 light-years from Earth and was discovered in 2011 using the transit method.
How Big Is Kepler-12 b?
Kepler-12 b has a radius of 19.66 times that of Earth, or 1.75 times the radius of Jupiter. Its mass is 137 times that of Earth, giving it a density of 0.11 g/cm³ — closer to gas planets like Jupiter (1.33 g/cm³).
Is Kepler-12 b in the Habitable Zone?
Kepler-12 b orbits inside the inner edge of the habitable zone of Kepler-12. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of Kepler-12: 1.167–2.738 AU (conservative: 1.478–2.596 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on Kepler-12 b
The equilibrium temperature of Kepler-12 b is about 1,480 K (1,207 °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-12 b — one full orbit around Kepler-12 — lasts 4.44 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.055 AU — closer to its star than Mercury is to the Sun.
How Was Kepler-12 b Discovered?
Kepler-12 b was discovered in 2011 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-12 b?
Kepler-12 b is 2,874.7 light-years (881.4 parsecs) from Earth. Light arriving here tonight left the planet about 2,875 years ago. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 50,594,720 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-12 b scores 0.05, ranking #5,293 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: Kepler-12
Kepler-12
- Surface temperature
- 5,947 K (Sun: 5,772 K)
- Mass
- 1.17 M☉
- Radius
- 1.48 R☉
Planetary System
Kepler-12 b is the only planet known to orbit Kepler-12 so far.
Kepler-12 b — Complete Data
| Radius | 19.661 Earth radii (1.754 Jupiter radii) |
|---|---|
| Mass | 137.30 Earth masses (0.432 Jupiter masses) |
| Density | 0.11 g/cm³ (Earth: 5.51) |
| Orbital period | 4.44 days |
| Orbital distance | 0.055 AU |
| Equilibrium temperature | 1,480 K (1,207 °C) |
| Earth Similarity Index | 0.05 |
| Distance from Earth | 2,874.7 light-years (881.4 parsecs) |
| Constellation | Draco |
| Discovery method | Transit |
| Discovery facility | Kepler |
| Discovery year | 2011 |
Data: NASA Exoplanet Archive, last updated 2015-10-07. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About Kepler-12 b
Is Kepler-12 b habitable?
No — Kepler-12 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is Kepler-12 b?
Kepler-12 b is about 2,875 light-years from Earth in the constellation Draco. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 50,594,720 years to get there.
How big is Kepler-12 b compared to Earth?
Kepler-12 b has 19.66 times the radius of Earth and about 137 times its mass.
How long is a year on Kepler-12 b?
One orbit around Kepler-12 takes 4.4 Earth days — short enough that 82 of its years would fit into one Earth year.
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