HAT-P-12 b
HAT-P-12 b is a hot Jupiter orbiting the K4 star HAT-P-12 in the constellation Canes Venatici. It lies about 466 light-years from Earth and was discovered in 2009 using the transit method.
How Big Is HAT-P-12 b?
HAT-P-12 b has a radius of 10.75 times that of Earth, or 0.96 times the radius of Jupiter. Its mass is 67.1 times that of Earth, giving it a density of 0.32 g/cm³ — closer to gas planets like Jupiter (1.33 g/cm³).
Is HAT-P-12 b in the Habitable Zone?
HAT-P-12 b orbits inside the inner edge of the habitable zone of HAT-P-12. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of HAT-P-12: 0.364–0.894 AU (conservative: 0.462–0.848 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on HAT-P-12 b
The equilibrium temperature of HAT-P-12 b is about 963 K (690 °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 HAT-P-12 b — one full orbit around HAT-P-12 — lasts 3.21 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.038 AU — closer to its star than Mercury is to the Sun.
How Was HAT-P-12 b Discovered?
HAT-P-12 b was discovered in 2009 using the transit method, with observations from HATNet.
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 HAT-P-12 b?
HAT-P-12 b is 465.6 light-years (142.8 parsecs) from Earth. Light arriving here tonight left the planet around the year 1561. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 8,194,560 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. HAT-P-12 b scores 0.09, ranking #4,532 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: HAT-P-12
HAT-P-12
- Spectral type
- K4
- Surface temperature
- 4,650 K (Sun: 5,772 K)
- Mass
- 0.73 M☉
- Radius
- 0.70 R☉
- Luminosity
- 0.2099 L☉
- Age
- 2.5 billion years (Sun: 4.6)
Planetary System
HAT-P-12 b is the only planet known to orbit HAT-P-12 so far.
HAT-P-12 b — Complete Data
| Radius | 10.749 Earth radii (0.959 Jupiter radii) |
|---|---|
| Mass | 67.06 Earth masses (0.211 Jupiter masses) |
| Density | 0.32 g/cm³ (Earth: 5.51) |
| Orbital period | 3.21 days |
| Orbital distance | 0.038 AU |
| Equilibrium temperature | 963 K (690 °C) |
| Earth Similarity Index | 0.09 |
| Distance from Earth | 465.6 light-years (142.8 parsecs) |
| Constellation | Canes Venatici |
| Discovery method | Transit |
| Discovery facility | HATNet |
| Discovery year | 2009 |
Data: NASA Exoplanet Archive, last updated 2014-05-14. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About HAT-P-12 b
Is HAT-P-12 b habitable?
No — HAT-P-12 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is HAT-P-12 b?
HAT-P-12 b is about 466 light-years from Earth in the constellation Canes Venatici. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 8,194,560 years to get there.
How big is HAT-P-12 b compared to Earth?
HAT-P-12 b has 10.75 times the radius of Earth and about 67.1 times its mass.
How long is a year on HAT-P-12 b?
One orbit around HAT-P-12 takes 3.2 Earth days — short enough that 114 of its years would fit into one Earth year.
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